50 Amp Solid State Relay design

I'm designing a high power power supply for a friend, yes its 5 years late now, I'm sorry, but it is getting there. What do you expect from one little engineer working part time!
Anyway, a big part of our problem is we prefer not to have relays arcing inside when they change ranges, and this is a real long way 'round to accomplish this, but hot switching DC is not always easy.
AC is easy because it has a zero crossing point, but switching DC without elaborate current diverting, and multiple layers of SCR's, I am not sure would be worth the effort or even possible.
It's a miracle the mosfets work as well as they do, I am very impressed with them and their capability, very much a rival to any good relay, however, the diode technology is going to have to improve a bit now to match.
I would not have thought something like this possible 10 years ago, but it is possible today, with some limitations, but it is very achievable! and that itself is exciting.