I love the EDR body shape... the bass i played fit me like a glove, and the guitar looks much the same... cool.
I've gone as far up as .68 in my seven with no serious problems- any larger than that, though, and you might have trouble getting the string through the tuning machine without drilling it out. I can't remember if I had to change the intonation, but this was in standard tuning, so...
XL scale would definately be preferable here, though... i do agree.
Now, if only they made an EDR long-scale guitar...
Hey, idea: buy a 5-string EDR bass, buy the lightest-guage bass strings you can (you'll probably need to hand-assemble a set) and tune it up to the pitch you would have had your guitar at... the pickups might be a little weak, but then again, if they're active... The results could be pretty cool.
(and yes, with enough saturation, distorted bass can sound AWESOME- a friend's fender jazz bass with a Boss metal zone into his bass head sounded just SICK. the Metal Zone is so over the top that it actually tightens up the bass a bit, giving you the same low-end impact but more "crunch" and compression. Tune that bass up a 5th to an octave, give or take, and you could get some sERIOUS grind out of it.