As a general answer to dual satellite reception, HD users here in the Caribbean usually resort to two dishes to get 2 satellites - futher south, the angle is just too wide to allow full strength reception (maximum signal - minimizing rain fade for BOTH 91 & 82).
Dual LNB's end up being used for multi-receiver setups... I've seen (and help set up) home-brewed versions of multiple LNB's mounted on bracket for HD on one dish - but there's always a comprimise for signal strength/priority. This is the case for either Echostar-type signal (Dish/ExpressVu).
If you already have a dish and have either a) a satellite finder/meter or b) local installer, best thing is to temporarily swing your dish and try out 82 as a test using your own receiver and noting signal strengths in the installation screens....
Finally, what has made life even more confusing, is that BOTH positions (91 & 82) have two satellites - N1 & N4i @ 91, N2 & N3 @ 82 - the reception footprints ARE different for each satellite AT EACH POSITION - I only have experience with 91 - but by experimentation, when tuning my dish, I've had to tune to a channel on N1's TP6 (I use 160) to "peak" the signal strength to an aim that is balanced for both birds. I'm sure that as you try to optimize for both 91 & 82, you may also find that gently/slowly rotating your LNB may yield improved results for reception of both birds at that position. (The purists may say that there should no need for LNB rotation with circular polarization - true enough for one bird, but if trying to receive two on one LNB, some skew is required... and hey, if it works....)