Flashing Skylight in Existing 1.5 in 12 SBS Porch Roof

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,

Did you torch down the SBS or is it really APP torched down?
Do you have a metal flashing for the curb already?
You can usually torch to the granular side if you heat the granular, trowel it down into the asphalt and then torch another sheet on top.
As far as X cutting the existing, I don’t do that but I’m sure others have their pet system.

ANS: SBS was not torched down - nail sheet (thin like felt) + cap sheet. Don’t remember if peel away or glued.

ANS: There is no curb and no flashing.

Your torch down thoughts, has given me one: I could torch the granular side and trowel the granules down into the asphalt - wouldn’t this now be a viable surface for more SBS laid up like chimney flashing? (minus the cricket of course - or maybe a shallow one with a 2" tall “ridge” for a 32x32in skylight.)