First, be advised, I have not used that dish for FTA, but being designed for their 3 sat service, and being on the 'small side' of what's advised for FTA - -
Possibly 'get signal' but probably not usable. At least don't think it would be dependable. (IMHO)
"DBS signals
are (a lot) stronger than FTA signals"
A 'stab' at it wouldn't be that expensive so trying it is within reason. But being on the roof, getting a receiver and television, yourself, electricity and tools up there, may present a problem if not a safety concern...
Better would be to test it on the same model dish, but on ground level. Convert one to FTA and aim the 'prime' LNBF at
101W . Then move the LNBF to receive
87W and measure your clearance to the center LNBF. See if the SWM allows it on their dish. Then maybe 'go for it'.
Oh, wait, if 87 LPB is what you're after, be advised, it's a weak signal and quite unreliable on my 30 inch Channel Master offset dish. Heavy clouds will make it pixelate and drop out completely in a light rain.
125W requires a 1.2m dish, now ,to 'get it all' here.