Big boots high flex advice

So I have been skiing from a very young age, and engage in club races at my college. But I am no professional athlete. Just like to go fast and have fun with it. I also happen to weigh 115kg or 250 pounds and am 198cm or 6’6”. I currently have 120 flex boot and really find them soft and limiting at times. I looked into some higher flex boots and find that race boots tend to cap at 28.5 ish mondo and this seems like I would not be able to fit even with boot fitting magic. I was looking at the fisher RC4 PRO MV which seem to be the highest flex boots I could find in 30.5 mondo which would be my size. Does anyone have advice or similar experience with this? Recommendations? I am also wondering about lace up liners and what kind of difference that makes?