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I started working on the WXB-F02 wing rigging and rear spar carry-through and I got to Step 17. Up to step 17 (after completing steps 8-11), I clamped the spar to the aft tunnel (via the shear plates) to ensure that the spar was sitting up against the aft tunnel. Once I drilled the aft tunnel to 1/2" (steps 14 and 16), I removed the clamps so that I could install the forward tunnel zee, wing attach angles and gussets. Once I installed the parts in step 17, I noticed that there was 3/32 of fore-aft clearance between the wing spar and the inside of the forward tunnel zee.
Is this type of clearance normal? I couldn't think of a reason for a gap that large, and I didn't want to start drilling the 3/8" holes in the forward tunnel until I confirmed.

Status update:
After lots of back and forth with Sonex around christmas and new years, they were not able to determine why I had a gap (which was unacceptable) between the spar and the tunnel.
Some key measurements that are not on the plans:
Expected gap between spar and tunnel: 1/32"
Distance between forward and aft vertical angles (SNB-F14-08 and -09): 3 37/64"
If I had to speculate where the error came from, it is probably in the pre-drilled holes in the SNB-F14-08 and -09 vertical angles (just my educated guess based on 15 years in the aerospace industry).

To fix the error, I fabricated spacers and installed them on the forward side of the tunnel.

Thanks for posting that update.