The barrel flex really only becomes an issue when the barrel is hot. As long as you don't get carried away with the trigger, you should be fine. One shot for a critter should hit where you aim.
A new barrel will be an expensive undertaking. A trigger job, smaller gas port bushing, and an Accu-Strut
will probably be your best bang-for-the-buck. Also, some believe that a pin on flash hider
will help stabilize the barrel a bit. It certainly makes the rifle look cooler.
Be aware that most of the accuracy problems were with the older Minis. The new ones are made on updated machinery and have had a few design tweaks. They're generally much more accurate.