[David Powell]

Not that I know much. You learn what's wrong with one bass by finally playing one that doesn't have that deficiency. I've played a bunch of basses, but not long enough to know except on the two I've owned.

1. The contour of the back of the neck: The first plywood bass I had this was wrong. It kind of came back to almost a point like the narrow end of a chicken egg if you cut a cross section through the neck. It made life miserable for my left hand. The bass I have now does not have this "mistake" It has a neck that is more like the other end of the egg, but perhaps even flatter along the back, like a classical guitar. It feels so good and so "right".
2. The nut height. OK this is a set-up issue and not necessarily construction, but too high a nut is painful in first and half positions. Low is better down to the thickness of a business card at least.
3. Shape of the upper bout against the body. If I lean down on my bass it just cradles my rib cage perfectly. It's that medium sloped gamba. May as well say a Josef Rubner gamba shape. That is what the maker now calls this model and of the Rubner gambas I have seen photos of, this shoulder is very close to those. I don't think I would like violin corners. I did try out a 5 string Christopher DB that had them and they were right away my most unfavorite feature of that bass.
4. Broad fingerboard with good space between the strings. I don't like the spacing too tight anywhere, particularly at the nut. This could be considered a set up issue but really it depends a good bit on the neck width. If I'm in thumb position I like to be able to catch at least two strings with the upper part of my thumb, so appropriate spacing there is important too. I probably like it wider than most players.
5. Upper bout width / depth: I'm thin with long arms so the upper bout and depth of the bass doesn't need to be narrow for me. I do like the shoulders to have some slope, but this can be restricted to the uppermost part of the bout. I can reach around most basses real easy. If I put the heel of the neck in my left armpit I can reach all the way to the bridge with my left arm. If the bass is smaller, it feels too small to me. On the 3/4 I could tap on the under side of the bridge with my left hand finger tips. My arms are way long for the rest of my size, so I need a bass with a somewhat longer body.
6. I like the bridge to be low down when I am bowing. This may be a German bow thing, but I have the endpin set so that my arm is almost fully extended when the bow crosses in the middle area between the FB and bridge. I usually play about an inch below the FB unless I am up stopping close to the heel.
7. FB arch and bridge. I might could do with a little more than my current bass has. It's a close call. I don't want to have to be wrenching my right wrist around too much to get at the BB string and more arch would increase that, but it would also make the E string easier to hit.
8. Thumb position: I like the way my current bass plays in thumb position. It has a really broad and not too much arch in the FB shape up there and the fingerboard has almost no scoop. This is very comfortable in this area. Flatter arch feels better for the left hand while steeper arch might make the right hand's work easier. It is a fine balance when there are five strings. Everything becomes more critical.
9. String height: I like that pretty low with almost no scoop. At the end of the board my strings are 6mm at G, 10mm at BB. The bridge is 6 5/8 tall from the center of the table arch to the center of the bridge arch.
10. I don't know what the overstand and angle are off hand, but when I lay my left forearm on the treble side upper bout, my hand falls so that my thumb is right at the octave.
11. Reference notes. The D neck is very good, but I still find myself "recuperating" from having played an E-flat neck for my first two years. I prefer the D at this point, but one thing I liked about the E-flat was that when I first started playing in a lot of horn keys, I could find the notes easier with the E-flat neck. To me the E-flat neck is the "jazz neck" and the D neck is the concert or rock-n-roll neck. The overstand point on my current bass is a perfect reference across all five strings for A, D, g, c, f. This makes playing at the heel easier for me if I am watching. On my first bass this was just a "place on the neck." That bass was not nearly the design quality of my current Rubner inspired instrument.
12. I like a swelled back. It fits better against my leg and torso and I like the vibration that is produced out in the swelled part of the instrument. My own feeling is that the swelled back is just structurally superior to the flat back. It will move easier when the wood expands and contracts and hold less tension and it will vibrate, stretch and contract easier with the rib flexing motion. A back needs to bend and one that curves has a head start.
13. Scroll. Why can't a maker get the scroll right? I've never seen one that was mechanically perfect. In fact all of them I've seen have the same mistake. Perhaps this is not a mistake to the makers. But to me, the scroll / pegbox design should not have the strings touching each other. It results in unnecessary wear on the strings every time one tunes.
14. Endpin / block. There is room for improvement here on most basses. I think Hamm is the only one I have seen that has done something intelligent in that area. He put the tailgut on a peg that pointed backward. The endpin was a separate thing.
15. Good night Mr. Smith!