You can NOT go UP in diameter. If you buy a 9MM you can not put a 40S&W or .357 Sig barrel in it. But a 357 sig or a 40 S&W can be converted to the other AND 9MM. Likewise you can NOT put a 45ACP barrel into a 10MM, only a 10MM conversion into a 45 ACP. The Glock 30 shoots 45 and the recoil is no problem. I had a Glock 21(45 ACP) that I converted and shot 10MM out of and the recoil difference was very small. Ask your G29 guys how they feel about 10MM recoil in the compact Glocks.
Never tried a Glock carbine conversion before. The cost is just too high for my taste. If you want a good 40 or 9MM carbine that uses Glock mags I would suggest the Kel Tec Sub 2000's.
