The 31 has an extra ring of panals that add anadditonal 5′ of hight; 40 more poles; and a large increase in volume. There is no difference in the materials used. Guylines if any can be added to the 20 clip clip cords at the 5′ high ring that circles the dome (see the online manual for info on guying; https://shelter-systems.com/lighthouse-manual.html also see the wind and snow warnings: https://shelter-systems.com/warning.html
On Nov 1, 2009
Dear Shelter Systems,
I am interested in your large dome for covering my koi pond( and hopefully allowing me to sit inside and watch them. This is something I will take down and put up every winter. We also get a moderate amount of wind in the location where it will be placed. I am very curious as to why there is $1000 (910 actually) dollars difference in the price of the 31′ dome vs the 30′ dome with only 14 sq ft difference in the area. Are there any significant other differences in strength or materials? Also if you could indicate attachment points for guylines to anchor against the winds, I would be very grateful. Thanks you for your kind attention to my questions.