Hodgdon lists 8.7gr. of 800-X as the max load for 180gr bullet, but at a modest pressure of 30,000 psi. So, if you're willing to go over book load, as many have, you can get great velocities with 800-X. I personally think it's the
high performance powder for 10mm in 165gr and up loadings, but Hodgdon refuses to sanction it as such. Like Taterhead said, it is flashy if that's a concern. It also doesn't meter well, so if you build performance rounds with it (which to me is the ONLY reason to load it), you have to weigh each charge. A lot of people don't use it because of that.
Running those top velocities in a G29 hasn't done much for me. It's easier for me to shoot hot 44 mag loads than hot 180gr. loads from my G29, and I shoot the 44 much more accurately, too. The issue isn't worse recoil with the hot 10mm, it's just harder to control. So, I stay away from the high end loads for my stock G29 carry, especially for SD loadings. But that's a personal choice for me, and I'm sure it will be different for different shooters.
Anyway, according to my data, using CCI#300 (std) primers, Starline brass, and 1.255" OAL out of a stock G29. 9.0 gr. will run right around 1100fps, 9.3gr will get you around 1150, and 9.6 will put you right around the 1200fps mark. I have gone as high as 10.0gr without any smiles, but that is an absolute max. load for my guns, and I wouldn't recommend it for a G29. 10.0 grains runs about 1220fps in the G29, 1295fps in the G20, and 1400fps in the G20 with a 6" LWD barrel. That load shoots great from my G20, but not so much from the G29.
I agree with what WeeWilly and Taterhead have said. Most 40 cal JHP bullets are made for 40S&W velocities, and you can easily run them too hot for good SD penetration/expansion performance out of a 10mm. The XTP is probably the best when pushed hard. You also want to have good accuracy and controllability, too. To me, the ideal velocity for a stock G29 is 1100-1150 fps, which is right in the performance wheelhouse of a 180 Speer Gold Dot. If I could get them right now, I would be running the 180 GDHP in my G29, propelled with a WLP and A#9, somewhere in the 13.5gr - 13.8gr range, to put it in that 1100-1150fps velocity range from the stock barrel. To me, that would be the perfect G29 SD load. Low flash, good velocity, good penetration and expansion.
Since I can't get the GDHP bullets right now, I carry Winchester 175gr STHP factory loads in the G29, same as Taterhead. They're less anemic than other 10mm factory loads, and you get the benefit of having a factory loading in the off chance that ever becomes an issue in a SD shooting. I don't worry about that too much, but if an overzealous prosecutor was looking to make an example out of you, and was able to determine that you used an "over book" load of 800-X, that could become an issue. So don't let anyone find out.