I do know you require access to Sats 110W and 119W or 99W and 103W for HD signals. I beleive 110W and 99W carry HD Nationals channels and 119W and 103W carry HD locals. Also 119W carry international programming like the Spanish ones available on the Para Todos package (latino). 101W carries all SD and the EPG.

You do not say where you live but 36" or 90 cm is probably way too big for most US cities. The Slimline3 dish or any oval-shaped dish , 24" (usually) with 3 LNBs and a bracket designed for either (101,110,119) or (99,101,103) will do the trick. I beleive 99 and 103 uses the new Ka band so maybe the installer has to use extra equipment or different LNB's.