I've had Russell's on three Beemers, a Rick Mayer on a KLR and a Bill Mayer on a C-14. My experience with the last one was the most recent ('08). It was in '04 with the KLR and prior to that with the Beemers. I have only had solo seat rebuilds since my wife does not ride.
On both Mayer rebuilds I had to send the seats back for adjustment but the time for the extra work did not affect my riding and, in both cases, the rework solved the problem.
Of the Mayer brothers, Bill's company is the probably the easiest to work with. Bill (Rocky) seems to have employees that can manage and do the work when he is out on the road at the various cycle rallies. At the time, I thought Rick was handling the operation pretty much by himself, but that may have changed since '04.
IMO, Rick's is a better design than Bill's because it supports the rear end more towards the outside edges (at the hips) and also under the thighs. Most stock seats don't offer enough support in those two areas. The rework on my Bill Mayer needed to give me more support under my thighs and firmer foam. The rework on the Rick Mayer was just to move me back a bit.
All three companies can rework a seat to meet my needs but, from my experience, I would rank the three companies -- Russell, Rick Mayer, Bill Mayer -- in that order.
'12 Guzzi Stelvio NTX
'09 DL650 ABS (Sold)