Thanks Erik. It is tough to beat aperture on deep sky, which has been the most difficult part of this - capping at 12.5, even though I do find 12.5 an ideal size for most situations. Although I'm not one of these guys that subscribes to the "aperture rules in all cases", there is a noticeable difference to me between 12.5 and 16. Not like 12.5 to 20, but definitely a nice step up IMHO. Theoretically of course aperture does rule, which is why professional observatories house larger and larger scopes. But when we amateurs don't have a climate controlled observatory to keep the equipment at ambient, with adaptive optics, sitting on top of a mountain at an elevation of 3,000m - 5,000m with perfect laminar airflow, we have to consider other things besides aperture. Your comparison between your 16 and the 24 down the street is perfect. The 16 is extremely tempting for me for a couple reasons. It's still easily manageable, will certainly cool faster than a 20, yet won't take that much longer than a 12.5, and it's still a bit larger than what I had before and will give me that extra punch when I do get to dark skies. In other words, I'll be glad I have the 16 when I'm out there, yet it's still workable for my main home use.
But whereas dark skies used to be 98% of my observing, right now it's 0%, and at most would probably be somewhere between 10% and 20% for quite a stretch into the future. So, for a killer planetary scope for home use, and observing some of the brighter DSOs, a solid-tube in my white-zone light-polluted environment, with neighbor's glaring security lights, the street lights, and school football field lights, is going to be much better than a truss for controlling glare and stray light. Not to mention it should be better at deflecting swirling air currents in my yard and helping deflect body heat, etc for planetary observing. My prior 10" solid-tube was much better at this than the 14.5 when I used it at home. I'm not saying it's impossible to do with a truss, but it is much easier to achieve with a solid tube. So if I do decide on the solid tube, the 12.5 is really the largest size I would want for that. Any bigger and it's just too much bulk to move around, and it won't travel well when the time comes.
Tough choice to make.
Oh, yeah. The Stifmeister's coming back to Grand Harbor. Deck the halls. Bye-bye, Great Falls. Wipe my a$$ and lick my ba!!s It's Stifler time, baby. Whoo-hoo-hoo. Whoo-hoo-hoo. ~Steve Stifler-American Pie 2