First rehearsal last night and it went well. I will play the 5er for the concert as it stands now. Playing those types of low passages on the 5er is much easier than on a chromatic extension. My stand partner has a Stenholm mechanical and had considerably more work on the keys fingering the notes down low but, didn't have a 5th string on the FB when not in use.
There is no perfect solution here when having to go down coming from the normal 4-string Simandl school. Two weeks after this concert I have another with a different Orchestra playing Beethoven's 9th. That one, I have played before with a C-ext. I tried it on the 5er a few weeks ago at a rehearsal and the string crossings are harder to do than the extension capo moves. Still not 100% on it but I have a rehearsal tomorrow and will decided from which ever bass I bring. I have the 5er in the case from last night but I might take the Hart and go that way. If I take the 5er tomorrow for the 9th, it's just to warm it up for the other concert in which I am using the 5. Or, give my left hand and my brain a break for a night and just take the Hart and switch back to the 5 for Thurs., Fri, and Sat's concert.