one other thing that I don't think has been mentioned is cutting a zag in the splice. a lot of guys make the frame cut in a Z. in other words, a cut down from the top thru the top flange and into the web of the C channel frame, then near the middle of the web, the cut jogs fore or aft, then jogs vertical again down thru the lower flange.
JML

 

The huck bolts/rivets are more or less outdated in the aviation industry in favor of fasteners that require less tooling. You could go for some Hi-Lok rivets....those are pin rivets that you fit into a reamed hole. They are finished off by screwing on a nut that has a shear collar...so you tighten until the hex head breaks off. You get perfect pre-load, but they can be spendy. I think you'd be OK with a bunch of grade 8 bolts that are properly torqued.

Here's a link for Hi-Lok fasteners: http://www.gen-aircraft-hardware.com.../pdf/hilok.pdf

Dan