Texan question

My thought would be to try the gun first as it is, and only then consider an upgrade kit. You may find that it has enough power where its at. If you keep your ammo under 300 grains, you may find that it has enough power to shoot those flat to a ways out. My brother's Texan shoots 218 grain HPs at the 900fps mark, which is just under 400fpe. 

If you go the AO way then know that that much power does stress the components of the gun (that is what an AirForce rep told me face to face). The frame is not that stiff so a Mad Dog stock should be a priority on a power build IMHO! By the way the AO Stocks are a direct rip of Mad Dog's Design.

I have a modified valve with a 3600 psi carbon fiber tank and a medium spring and with that set up I am your feet shy of the 4500 psi set up that you asked about a lot less stress on my GUn . Example, 335 grain slug/905 FPS 260 grain Aeromagnum 1009 ft./s 

I also think you outta try the stock rifle for a while. These are powerful rifles out of the box. 

I have a highly modified 45 Texan and I too recommend shooting it stock a bit before doing anything like the AAO kit.

The only early mod I might recommend is swapping the Air Force aluminum tank for a TalonTunes 3600 PSI carbon fiber tank even if you are not using the extra pressure fill (at first).

+ on stocking the rifle, it totally changes the shooting experience for the better

The NSA 350gr slugs are MOA shooters at 100 yards in mine but I have actually gone to lighter bullets in the 280 to 300gr range



I am going to say that the advice of a couple of REAL experts, not just internet keyboard warriors, was the AAO kit might be right at the red line on the strength of their valve at 4500 PSI (not even mentioning the gun itself here). I am a push the edge of the envelope 'first adopter' guy but I do make an effort not to go over the line to 'experimental test victim' so I will wait a while and let more people go first on that one.