I'm at a loss. This is going to get long and complicated... sorry I have to travel to rehearsal by bike, so can either leave bass where we rehearse or carry it on my back. I've had bother with RSI and find a bigger body bass gives more support and enables me to adopt non-damaging hand positions. I haven't decided whether it's best to do daily practice with the instrument I shall perform with, or weekly practice in the band format/volume/venue I shall perform in. I'm going round and round with circles with this. The only sensible answer is to get identical basses, but I'm sure you appreciate that that isn't any fun for a GASser without much money.