GNeJ, if you have an unused frame around and are just dying to have a 9mm 1911, go for it. On the other hand, I have to say, why bother.
If you put a 45 ACP slide on it, you will have a much more flexible gun.
I have one load using a Penn Bullets 152gr dual ogive LSWC that makes 142PF. That's in the same league as the 147gr 9mm rounds (144PF) I used to shoot in my Sig P226. And, it is way more accurate than the 9mm was. It is accurate enough for Bullseye use.
I have another superb load using a 200gr LSWC load that makes 134PF and is softer shooting and more accurate than any 9mm round I've ever shot.
A Nosler 185gr JHP at 775fps gives you one-hole groups at 25 yards with a 143PF. That's squarely in 9mm territory.
Using 200gr LSWC at velocities giving PFs from 155 to 160 really, really kicks up the accuracy and consistency. SDs in the single digits are easy.
My major, 175PF load uses a 200gr TCPB lead bullet and gives SDs under 7.
Then you can go to 180PF for hardball matches or use full bore factory loads.
So for me, It made much more sense to sell the 9mm and stick with the 45. It is much, much more flexible.
BTW, I also tried the one frame, two slide approach. I'd caution against it. One of the slides cannot be fit as closely as the main slide, and that slide will show rapid wear (comparatively speaking). The only time I could recommend two top ends is if one of them is a 22LR conversion unit.
BTW2, these comments are for single stack 1911s only. With 2011 frames, it is a whole 'nother story.