Nahh... just get a nice 6x12cm Horesman back. Use PS to sticth if you want. You can keep what you have and utilize sheet film later if/when you want to. You'll keep all your Scheimpflug movements too. It's the best of both worlds. I bought my Chamonix 45N-1 specifically to shoot 6x12cm roll film and doubt I'll ever shoot 4x5" with it. If I want (and feel well enough to carry it) I'll shoot 8x10".
Gee whizz, man, you can buy a NICE 6x9 RFH for less than $100US or a decent one for around $50US.