Let me just ask, why don't you like split grip rods? playing devils advocate here is all. is it strictly looks or is it function? on a spinning rod, my right hand (casting hand) rarely, if ever, touches the rear grip. sometimes when I really want to send it I use my left hand to provide more leverage on the butt of the rod, but the butt cap would be there so why do I need all that cork in the middle?
I build my rods with both split and full rear grips. Lately I've been building a lot of rods using Winn grips in lieu of cork. On a spinning rod made for targeting slot drum I'll use a 2.5" butt, a 1.5" rear grip, and a 2.5" fore grip. I highly doubt this adds any technical advantage to that rod, but I like it. On a rod made for bull drum though I use full rear grips, either Winn or cork. truthfully I don't know why but that's how I prefer it. To me, lite rods get lite split grips and larger rods get full grips, but I doubt there's any technical advantage to either in real world application.
Heck if you want to get real weird, don't even have grips, just put a butt cap on it and some winding checks on either side of the real seat and be done. Your holding the real seat most of the time anyway. spend that extra money on a real seat that feels like heaven.