i've never tried it and i know it's not in the armorers manual. i would not reccomend it. Glock mags are not user friendly and i would not reccomend opening the magazine lips either. i would stick to the factory 10 rounders if that is all that you can find. with todays conventional ammo, 10 rounds with a spare mag should be more than efficient.
glock 17 is a large fun and they are nice. i guess it's all in what you want. as an leo, i can buy hi-caps for 20.00. i guess if i couldn't thought, i would probably not have the glocks that i do. you could have bought a P11 and saved a ton of money.
I would NOT trade the G-17 for a CZ.
Yep, you can get cheap aftermarket mags... and they're pure garbage. You're going to have to buy factory mags if you want reliability... and then you're right back up to that $100 range again. It's like having a Beretta 92F... they come with ten-rounders, but you can get fifteen rounders from other makers cheaply... ones I wouldn't trust to take groundhog hunting. Only factory mags work properly in almost ANY gun.
Besides... the Glock is a better gun than the CZ.