Hi Das, welcome to the OLF.
Since it is an electirc, why not stick with the accepted 25 1/2" scale length? I would think that should work fine, and you wouldn't have much trouble finding fingerboards already cut to that scale if you choose.
Radius is whatever the customer wants.
On the one 7 string I built, I had a nightmare with the customer.
First he wanted a 16" radius. Made the guitar that way.
Then a 14". Went back, and redid the guitar THAT way.
Then finally a 12". I pulled out my hair, the re-redid (not sure what that is in French) the fingerboard.
The problem was the stretch, and what the player can (and cannot) be comfortable with.
Good luck, and again, welcome.
Steve
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From Nacogdoches...the oldest town in Texas.
http://www.stephenkinnaird.com