Stanley,
Merry Xmas.
I know there is a school that says that fishing for GTs in Southern Oman requires minimum PE 10 and locked drags and I can see the rationale given that fishing there typically means hooking big fish in shallow water. There are some anglers who advocate that style that I could not hold a (Xmas) candle to.
However, I fished it fine with PE8 and caught decent fish up to 127cm (admittedly with an SW18000) and intend to fish it again soon using the same gear. I'm not sure I'm capable of working anything bigger efficiently enough to really get the best out of the fishing over 5 days. I fished with one guy who got some big fish up to 143cm on a Race Point 200, PE6 with a Stella 10000, so there's no hard and fast rules although I would not advocate fishing that light. There are times when you have to get lucky, palm the reel to stop fish and there will be times when you won't stand a chance no matter what you or your captain does and just get smoked but that will also happen on 150lb (albeit less often!).
The best bit of advice is make sure your gear is in top shape...reels and drags serviced before the trip, guides and seats on the rods checked, premium extra strong terminal tackle and hooks and your knots 100%. I think that's much more important than whether you're fishing PE8 or 10.
Just my thoughts.
Regards,
Trevor