If you need something that does a better job of filling your hand, I'd look at the AX - it's quite beefy and will fill ANY hand. That said, I have fairly large hands, and while I noticed the dangling pinky phenomenon on the RX as well, I got over it pretty quick. I think the RX is one of the best designed SLRs ever made.
Another option would be a 167 MT with the PB-5(??) battery grip. While the battery grip on the 167 does not have a vertical shutter button, it does give you a good grip for vertical compositions, and balances the camera better. It also moves the tripod socket to the center, not the end, making it, in my mind, a required accessory. I used to shoot a pair of 167s before switching to an RX.