Thanks guys.
Canoe
-the clamps are just made from thin scraps of wood. They vary a bit in thickness, but are about 1/8" thick. They're the biggest I could get from the scrap I had- 1 1/2" high or so, and about 7" long. The little notches on the side are, I believe 3/8" square.
-no twist, just offest. Oddly enough, they look almost identical to a RW feather glued on with an actual jig. I got the offset really simply: I squared the sides of the slots up with the sides of the hole. So in front, the slot is flush with the right side of the arrow, and in the back the slot is flush with the left side of the arrow.
- about 7" wide, 6 1/2" or so long. It's about 1 1/4" high or so. It would be better it were longer, but that's all the longer I had my clamps.
-No slots. The front end, in front of the fletchings, is just attached with two small snubbed 1 1/4" screws. It only takes three or four turns of a screw driver to take the front off, into which (and out of which) you slide the arrows. COuldn't think of anything better than that at the time
- Some of the slots are a bit larger than the clamps, and so I jut shoved some little shims in there to keep them still. Gives me a little wiggle room too.