frame of mini-halfpipe,need help

[skate10]

Help!
i'm helping my son(10) build minihalfpipe with your plans,(the video is awesome). We adjusted the frame to a rectangle of 4x8 instead of square 8x8, and we are using 2x4's instead of 2x6's. We cut the inner skeleton to 3' x 9" on all 13 pieces and left the outer frame pieces at 8'. We screwed the two 3x9" ends inside the 8' pieces to form the rectangle. Measuring from corner to corner on the diagnol is 103" and the other is 104". It seems that all the other 3'x9" pieces in between are too short, except the 2 that were used on the outer edges? WHY and how can we fix it?
thanks for help getting us started.

[skate10]

ok, so home depot cuts weren't perfect. Will need to recut wood... unless, would shims work? There is up to a 1/2 inch gap on some boards.

[Bobby]

Hard to say, 1/2" gap might be fine, after you screw in the plywood things will become more solid. But if you don't see it as too much work it might be worth the better fit to get better cuts (keep in mind you will have to cut to better precision than home depot did, 1/4" off on two pieces next to each other can give you 1/2" gap).