Welding it's cheap, so do it now and see how you like it. You can always yank it out and put a detroit in it later if you want or as $$ allows.
I honestly don't know if the spool kills my turning radius much compared to a detroit, since I have never run a detroit in the rear, but the front tires hitting the springs and killing my steering radius. When I spooled the race truck I don't think I noticed much difference.
It would be fun to find someone with a rear ARB and do a little testing, see how much a rear 'spool' really does effect turning in various terrain.
If I can drag a Scout through many of Reider's trails with a rear spool and not tag many trees, Crusty in his heep and you in your Sammy should have no issue :flipoff: