No. The only "neighboring structure" would be the house itself, and believe me, the Boss would not put up with it. That would also run the "stealthy" aspects of it.
Sometime in the next few days, I'll get my hands on some modeling software and try a few things. I'm not ruling anything out, so long as it physically fits inside the fiberglass & isn't overly complicated. Roughly 22 feet of wire inside the flag pole, plus another foot or three (give or take) to get to the SGC tuner, should load just fine on 40 & 30 meters for certain, and a high probability of 20 & 17 without too much difficulty. So the worst that might happen, if 12 & 10 turn out a little flaky on this, is that I retune the Solarcon, or keep using the Butternut on the high bands.