You have already touched on the reason as to 'Why Not?' [
] Weight.
These AC are designed to fly with certain weights IF you increase the weight they do not fly - very well - [&o]
So - what am I talking about? The performance of the AC. If you increase the fuel from 10 - 14 oz ... fine you just bought yourself and extra 5 minutes of flight time - BUT the first 5 minutes thw plane flies like a brick because it is too heavy. [:@][:'(]
You will spend this time lumbering into the air (If you can get off the ground) and then any manouvers that you do will be slow and sloppy. Once you burn off some fuel - the responsiveness of the AC will improve dramatically.
I see this with my AC daily, I can do some manouvers only after 1/2 a tank has been burned.
Your call - Happy Landings