RE: WM Dago Red Engine choice...
With a YS 110/115 or YS heli 91 you WILL need a Sullivan Cylinder 16oz for decent flight time. It would be a good idea to double or even triple some formers or bulkheads to retain the strength because of how much material must be removed to fit the tank. The tank cannot rub on any thing hard as this will in one flight put a hole in the thin tank and flood the electronics thus kill the plane! I have seen this happen twice (not to me ) These engines produce a lot of vibration, I've seen wing tangs fiction burnt, thin brass sheet on one side the joint stops the wood from burning. Back to the tank. Don't use the cheap or questionable import tanks that could fail under pressure. To keep the tank's neck from splitting when I crank down the stopper, I like to wind some tight wraps of Kevlar thread around the neck of the tank and lock it down with thin CA then protect the CA with a thin coat of 15 minute epoxy. (most 5 minute epoxy is not fuel resistant). Use a Sullivan heavy duty multi fuel stopper kit (blue anodized). Some tanks are very hard to install the stopper because there is little to no chamfer, so with a sharp Exacto knife cut a SMALL bevel. Wet the stopper with spit and it should go. Box or rectangular tanks sides can swell when it gets pressurized so allow room if you go this route for your needs.
Hayes tanks are very strong too.