That is a gorgeous picture - congrats on growing those beauties. Its too late for this year, but a couple of suggestions: Peony rings with the criss/crossed grid inside the round frame - will hold up the lower stems and the plant grows right through it. you can get these really tall. Tomato cages work also. Ditto the linking stakes that you sink in the ground and then have like a hook and eye attachment - you can make your circle any size. wooden stakes or green bamboo and string will loosely hold up the billowing stems and you can get them in place after the flopping starts if you have a helper. I use 8 ft green bamboo stakes and green garden twine to tie up some things like dahlias, Lilium Black Beauty - 7 footer. But the very best holder upper I've ever found is the plant itself. If you haven't read Tracy diSabato-Aust's book called the Well Tended Perennial Garden, she describes in great detail how to pinch or prune plants to make the plant more compact and delay blooming. I have started to cut my heliopsis in 3 layers, kind of like a wedding cake - shortest on the outside ring, then another layer that ends up about 4 ft tall. The center is left alone. This doesn't have to be so exact because I want the plant to look relaxed and natural, not rigid and defined, but it does prolong the bloom time and also the outside rings hold up the center on what has become a very large plant.

Try to bring the end studs down below the subfloor so you can nail them off into the floor joists. If you can build the wall adjacent to a joist, great, nail off onto that. If not, then install blocking between two joists (the "X" pieces) and nail the studs off onto the blocking. The blocking can be one large piece (like a 2x10) or it can be two smaller pieces (two 2x4s or 2x6s). For illustration purposes I showed two pieces of blocking. There are certainly other ways, and there are variations on this method. This is just one permutation.

There are some good ideas here. I tend to have a lot of clear glass punch bowls too, and several lazy susans which work out well. Long ago, I started collecting inexpensive clear glass items for my tables, so the food would be the star. Another thing I figured out a long time ago, is I can serve out of the same vessel the dish is cooked in, especially if it's fabulous. I invested in copper cookware, which I love cooking with, and because they make equally great servers. I've never needed a soup tureen, because my hammered copper soup pot is so beautiful. (It's also a double duty thing, which helps keep storage to a minimum.) I've been known to serve salad out of a bag with a brightly colored scarf tied around it, or use a fabric runner on a table for food, so I think you can use anything you want really. In my current stack of stuff, I also have a couple of colorful enameled and SS dishpans, and some restaurant supply bowls, which I use mostly for prepping. I'll fill several platters with the same food as well, which can be replaced easily during the event. Also helpful are bowls/cake plates on pedestals, which help save refrigerator room by using vertical spaces.

Wow thats pretty large. Glass and grout adds a lot of weight and might possibly compromise the windows strength. I would want to consult an engineer before I did something that large. Perhaps doing somewhat smaller pieces in frames (like say regular windows) and mounting them on chains to hang in front of the windows is an option. On second thought-are the windows purely that size altogether -one large piece of glass? Or broken up-several windows adding up to that size?