Mmmm I could wade in so long and so much, but a tank that flexes is best in my opinion...and I have done a little jet flying. BVM were there (possibly) first with composite tanks-you think uncle Bob would have missed the trick of developing a hard walled tank if he thought it was a good idea!?
If the tank sucks in its nothing to do with the bottle, its the plumbing that's wrong. Free flowing the plastic bottle works great...most important it informs you of what is happening during the life of a fuel system and model. It should not suck in or bulge out in use, if it does you clunk, clunk line, fuel lines, overflow is inadequate...simple fact. A hard tank masks this fact and the first time you know about restrictions it as a flame out. I have seen this enough since these "hard walled" tanks became a "bling" item. Heavy! multiple leakage points. Funny enough my latest RCJi article talks about this.
MAP Canada make the best hopper, bubble, UAT, trap. They have hi-flow, std and small, everything I need and having sold hundreds and hundreds to happy customers and used them exclusively in every model I have built for around 5 years...smart people notice how many flame outs I suffer...one hand will do for many many many hundreds of flights, and the few have been nothing to do with my hopper tank choice or fuel system.
Mounting one is easy...and light,depends whether the operation of your model or the look of your installation is key.