Converting a standard 1911 mag to fit Hi-Point's JHP is really quite easy. A picture is worth 1,000 words, so watch the video, then go DO it.
But if you are on dial-up, or if ya just like to read, then I'll briefly describe it below...
There's not much difference between the JHP mag and a std. 1911's. The JHP mag well is slightly wider, so your 1911 mag might rattle a bit, but never enough to bother me, even when hunting. The main difference is that the 1911 mag catch goes into the mag, so nought but a slot is needed; but the JHP has a bit of a rise in the metal just above that slot, so the mag catch doesn't need to enter the mag.
Soooo, what we're going to do is basically create that rise, a small tang:
1) relieve the metal a bit on either side of what will become the rise. I use a narrow cutting wheel on my Dremmel. It doesn't need to cut all the way through the metal, but just enough to weaken the metal so you can bend it...
2) bend the metal to create a tang (our rise) above the slot where the 1911's mag catch would fall. I like to use needle-nose pliers, but any pry tool will do. Be careful NOT to accidentally press in below the slot while you pry-up above it (we wouldn't want to slow those .45 shells on their upward travel through the tube!).
3) there is no three, you're DONE already.
If you find the mag drops out when loaded, or when fired, then you may need to bend the tang a little higher, so it more fully engages the JHP's mag catch.
DON'T go measuring the particulars of the mag geometry & comparing HP to 1911, it will only frustrate you. The fact is there are some true differences, BUT they all seem to work in our favor. For instance, with the HP mag you shouldn't slam a fresh mag home while at slide-lock, cuz ya might bend your firing pin... BUT the 1911 convert doesn't raise the mag as high into the slide, so there's plenty of room between your shells and the pin. Besides, the butt of the 1911 mag seats BELOW the bottom of the HP grip, so smacking the mag with the heel of your hand is only gonna drive it so deep, ya really need to thumb it into place to make sure you're seated firmly.
I personally like the 9rd mag our beloved mothership delivers, but for those who want a little less, for concealed carry, etc... then here's an opportunity. Keep your eyes open, you can usually pick-up 1911 mags at a gun show for $8-12, so you can have a lot of spares for a little cash.
(AND, special thanks to my son Nathan for the video shots and for editing-out the phone calls & "is it running?" verbage)