gas also is much more fuel efficient so you can fly with less fuel for the same duration. This largely offsets the alleged increase take off weight.

the higher weight of a gas engine is important to consider when balancing the aircraft but take off weight is what determines performance.

Gas is also less dense than Methanol; specific gravity of 0.745 average vs 0.79 average.

so compare weights, check how much fuel volume you need and you'll see take off weight difference is negligable compared to the amount of thrust available.