All depends on what size conduit you're using I suppose. My dome is 3/4' Freq 2, and it can hold 300lbs per vertex easily.
I know Robotland (sorry. I've met you and am totaly blanking on your real name.
) stacked a few domes kinda like that with a platform and it was rock solid. I had a small platform on my dome as well (some 3/4" ply over one of the top triangles).
You shouldn't have any trouble at all. I think you'd be very hard pressed to break a dome.
My real handle's Steve, or Planet Steve
to be precise...A friend nicknamed me years ago, after noting that I had enough scrap and crap and funk and junk to construct my own planet. "Planet" or "Robo" are fine, too. Jes' don' call me late fer dinner.
Regarding the "Snowman", and dome platforms- I designed the "fiesta deck" for the Snowman (so called from its resemblance to three stacked balls of snow) by the seat of my pants, and have no clue whatever about measurements of stress. But I had eight or nine folks up on it without a wiggle. The first incarnation started when I decided to put a 6' rad. dome on top of the 9' base-dome- I added special right-angle junctions that bolted to the five vertices of the top pentagon of the base-dome and that each had two struts that bolted to two of the ten spots around the "equator" of the top-dome. To prevent wiggle, I added horizontal struts from those equatorial points to the "North Pole" of the base-dome....And then realized that I could add a platform. 3/4" conduit would bend under the load, so I used conduit clamps to fasten on 2x4" radial beams and then covered those with several experimental surfaces...More 2x4s, cut to form a pentagonal deck like some fancy picnic table kits, plywood, plastic pallets...The final version had wedges of scrap plywood with 2x4 sections screwed and glued on, that lay onto the conduit and were bolted together for safety. Then I added a 16' hybrid stairway/luge track that featured a boat chair on runners. Wheee! Scary ride, with the runners soaped up! At week's end last year, Dragonfly Jafe was kind enough to give the wooden bits a ride (on the Tongue Car!) to the burn platform for sacrifice, so I didn't have to drive 2,000 miles home with the stairway poking me in the side. This year, a much lighter and more portable dome-structure-vehicle-hybrid is in the works. And I want to try the Parade of Domes idea again, with a little more organization on my part- Ironically, ditching MY contribution will probably make that possible!