Thanks for all the responses. I wasn't meaning to complain about my tripod - I'm quite pleased with it overall, and would recommend it to other people looking for a CF tripod. It's just a specific use that I hadn't thought much about, given that I didn't own a macro lens until a couple weeks ago.
You guys all had some good points that I hadn't thought about (especially about how I might want the intact column later, even if I don't use it much now). I can always buy a replacement, but they're not cheap. I will say my concerns (when upside down) aren't about stability - they're about whether I trust the head+plate to hold with a 2 pound camera and a 2 pound lens hanging from them.
😀
I realize it's probably silly that I'm uncomfortable using the reversed column - after all, they wouldn't design something that'd drop my camera, right? But I just couldn't relax with my camera hanging there, upside down...
😛 The other issue (that may just be due to unfamiliarity with using it that way) is that, upside down, the legs tend to get in the way a bit. The 70-180 macro is a fairly large lens, and setting everything up so the lens isn't against a tripod leg means the viewfinder of my camera is next to a tripod leg. It's a bit awkward.
🙂
Abstract, I had been thinking about trying a different Manfrotto short column just to see if it works. But then someone else just pointed me towards this
low angle adapter. I didn't know this even existed - I'm going to give it a shot. If I'm not happy with it, I'll try shooting "upside down" a bit to see if I get more comfortable with it - I might have to keep a pillow around to place underneath, though, just in case.
😀