A minimum would be to replace the liner (preferably with a teflon liner) and to select the proper contact tube for the end. U groove rollers are better than Vgroove.  Having your local supplier modify your gun to a minumum length (6 to 8 feet) would also help reduce the frequency of bird nests.  5356 filler is slightly stiffer than 4043 and may also be a slight advantage with this kind of setup.

Note that aluminum does NOT like to be pushed through a long whip or a whip with any sharp bends.

This kind of setup does not lend itself to high output production.

If you are going to be doing much of this type of work it is best to invest in a push pull or spool gun.