The percentage pay applied to the front line, but the back-line guys were on a fixed salary. Not really sure what that was, but it was apparently sufficient to keep sidemen happy for many years. I know Ben Schubert and Tom Green worked with the Trio for at least 20 years each. Ben probably longer than that.
With the Brothers Four, we were all equal partners, so all overhead expenses were taken off the top and then we split the net among the four of us.
As to the comment that Nick "knew what he was going to earn" - well, I always did as well. We would be informed what the gross pay on each gig was and we could calculate our percentage, so I always knew in advance what my pay on each show would be. Now, obviously I don't have first-hand knowledge of Nick's deal with Bob, so perhaps he was on a fixed salary, but that would surprise me, knowing Bob as I do. Perhaps Nick requested such an arrangement, but unless his "fixed salary" was higher than the average he would've made on a percentage basis, I can't imagine that he would prefer that policy.