See your other post on Hi Std's, as to why you should not shoot anything but Std Vel ammo in your Hi Std.
When you up the recoil spring you move the slamming from the frame's slide stop to the face of the slide. In very short order the front surface of the slide will show signs of hammering. Stick with the stock 5.5# spring or the varible rate 6# spring from Wolff:
Brownells has the stock recoil spring as supplied by TX Hi Std:
You can also go directly to the TX HI Std company for parts but they are all available at Brownells under their OEM parts section. They are the same parts, exactly.
Many people have been down the path you are traveling, including me. I suggest you stop and go to the Rimfire Central/High Standard forum and get educated before you hurt your Hi Std pistol. I have several Hi Std pistols and had to learn the hard way as to how to treat them. Fortunately I have not cracked a frame but many others have.