THere is no need to go to RG11. I'm running approximately 250' and don't have any problem. I'm using RG6 from ribbon cable on my main dish, but also have a
DTV dish with plain cheap Radio Shack RG6. At one time, I even had 175' of the RG6 ribbon cable spliced to about 75' of RG59, and even that worked fine, but I replaced that with 250' of ribbon. The only time I've had problems, has been with the
Twinhan Starbox receiver, which has very poor sensitivity, but I have a splitter between my analog receiver and my digital receivers, and a
diseqc switch going to a Fortec Ultra, going to a Twinhan 1020a, going to either a Broadlogic card or a GI 4200 DCII, and all these receivers have plenty of signal from 250' of RG6.
These are NOT weak signals that you need to worry about signal loss. Since there is an amplifier in the lnbf, these are really pretty strong signals.
Anyway, I can't comment on longer than 250', but up to 250' I wouldn't worry about signal loss.