The Regal is pretty hard to beat the way it is. The Slingshot hammer gives it an almost regulated shot string on top of the curve. I tried one of the Altaros drop in regulators but without other significant mods it wasn't a good option. Jimmy
You could always tether your Regal to a 90ci Air Venturi carbon fiber bottle/fill station sold by Pyramid Air. The bottle output is set at 2900 psi (200 bar) which in my opinion, is the sweet spot for most PCP rifles You could shoot for an hour before having to top off the tank which is a huge bonus, especially with the Regal which has a fairly small 132 (Huntsman Regal) or 162cc (Regal XL) air cylinder. Another perk is you wouldn't void your Daystate warranty since you wouldn't be modifying the actual gun. I used this setup with my Wolverine 303, Impact ,25, and Air Wolf..22 and it worked very well.