My experience with scallops has been:
- Scallops don't have to be nice and symmetrical, because they basically take the fingerboard out of the equation. Granted, you want everything to look nice, but if you start modestly and slowly, you can usually get it good enough.
- You don't need to scoop out that much wood. Go slowly. The Dremel contour sander is a good tool for this.
-I haven't tried Blackmore scallops, but I don't see what advantage they would offer. Even with 9's, it's damned hard to push the strings out of tune, especially on a 25.5" scale guitar.
-For me and the way I play, scallops are unnecessary. I scalloped one guitar, and it is a fun experiment. I practice on it all the time, and I've found that it has lightened my touch and made me a more nimble player regardless of which guitar I play.
I guess what I'm saying is, if you're interested in scallops, skip the half measures and get a full scallop neck. If you don't like it, you shouldn't have any problem getting your money back on ebay.