Are you looking to run major or minor in open class? If minor, magna porting may be ok by itself, but you will be at a huge disadvantage to the open major guys in scoring. If you plan to run major a good comp is going to be way more effective than magna porting alone. If you still want to magna port be careful what you have done, as holes in the barrel bleed off pressure way faster/sooner and may make it harder or impossible to hit major. You would almost have to have your barrel throated also as the short CZ chambers limit how long you can load most bullet profiles, and you will need all the length you can get to get enough powder in the case and still seat a bullet on top.
I shoot a P09 in open class with just a 3 port comp, no holes in the barrel. Its a ton of fun, if you aren't trying to make master class I would leave the barrel alone and just get a good comp. If the bug bites hard you will end up finding a real open gun any way, if I come across a steal on a czechmate I'm going to upgrade.