Tempted to cut a hold a glue down a polycarbonate dome since it is a porch where insulation and leaks are not a disaster, but also considering a proper install.
8-10in curb is what I'm guessing is good since in SW PA and we easily get 4-6" snowfalls annually and 12" every 5-10 years and 18-24" every 20+ or so.
Best use of existing SBS would be to mark corners of the curb outside dimensions, cut a big "X" through the SBS & nail sheet, then peel them back and up the wide of the curb.
But that leaves the flashing and the issue of sealing on top of granulated cap sheet.
Thanks in advance, any help will be greatly appreciated,