> Is this bad? Should I go into the side panels a little, or should I plane
> only the outer parts of the sheer clamps and end up with a narrow gluing
> surface?

You can plane into the side panels a bit as needed as mentioned in the other postings. I had to do this with my Ches16. One important note though, is to plane the sheer clamps at the correct angle, but flat, not curved toward the outer edge. This prevents the need to actually bend/hold the deck over the short width of the sheer clamp, which is nearly impossible to do. Flat angled sheer clamps if planed correctly will produce little to no gap where the deck meets the side panel.