Didn't I answer this in another thread?
Since the adapter needs a PAL cart in the back to play NTSC games on a PAL console, that means it's using the lockout chip in the PAL cart to boot the NTSC game. That means that it should work in reverse as well, with an NTSC game in the back to play PAL games on an NTSC console.
For US games it wouldn't be necessary with an NTSC game in the back of course, and the adapter works as a passthrough device instead.
So to put it simply, yes it'll work. I haven't actually tried it myself but I don't see why it wouldn't.
Edit: Well I tried my booting a PAL game with my AD-29 Universal Adaptor on my Super Famicom and it worked fine. I used to use that adapter to play NTSC games on my PAL SNES before I got my SFC. My SFC is region modded though, so it can boot PAL games on its own as well.
Edit²: Ok! So since i have the Super CIC mod in my SFC, I put the console in auto-detect-region mode. Then I booted my PAL cart of Mega Man X. As expected, it detected the region as PAL and put the Super Famicom in 50hz mode. Then I used my AD-29 adaptor, put Mega Man X in the front and a Japanese game in the back. Now it detected the region as NTSC and put the console in 60hz mode!
So yes, I can confirm that it should work.