I made a similiar frame from pvc years ago and its still going strong. If it will help, several points that have worked well on my frame...I drilled 2 holes in pvc center ridge about every three feet
for 3/4" ribs which pass though center ridge and connected 2 pieces of the 3/4"
rib material as needed then cut to desired size , they fit into holes in pvc that run along
(inside) port and starboard toe rails.(ribs and all numbered) This creates tension that works well and can be carried all the way back to the stern. Another big help is using plastic ties to hold things in place when setting up and from wind, come spring they cut off real easy.
Pretty strong, stands up to wind and snow.
Hope this helps.... Hugo