Fingboard position markers.

[JackStraw]

Hello everyone. I'm in the process of building a weedwacker upright and have a question about position markers on upright basses. I know many (or most) don't have markers at all, but i've seen some with markers along the side. I'm not at all familiar with playing on a 40" scale (or fretless for that matter) so i plan to put marker inlays into the fingerboard. However, if i'm going to do it... i want to do it like a professional luthier would.

On a fretted instrument i would put them directly between the frets, but on a fretless instrument i'm guessing they go exactly where the fret would be. Is that correct? Also, at what intervals is typical? On a fretted guitar i would normally do 3-5-7-9-12, then repeat. Is it the same for an upright bass?

Thanks in advance,
-Jack