I have one thought about the OP's concern about there not being enough mass behind the chamber. If there isn't enough mass behind the chamber of the CZ, then there isn't enough mass around the chamber of the Tikka.
The Tikka is really a clever design. The first Tikka I ever handled was at Scheel's in Billings. My first impression was that it could be a stamping. The bar stock receiver appears thin to me comparatively. I'm not trying to suggest that it's not as strong as any other comparable rifle. It would have to be to be sold twice.
By comparatively I mean that I own, right now just three rifles. A Weatherby MK V, 340WBY, Vanguard 300wby, and a Cooper MDL22 6.5-284. These all heavier designs.
I wish I was young and tech savvy and could post a link. There is on Youtube on a video called burst test. I saw this years ago with out the music and with the data. A 180 gr bullet is lodged 8" into the barrel. A 300WM is chambered and fired. The rifles tested were from A to Z. Blasers to Vanguards. The results were interesting. Three failed, two catastrophically.
Anyone firing the two that failed the worst would have been maimed or killed.
I think you will happy with either the CZ or the Tikka. I think it would be hard to go wrong with almost any rifle on the market today. They all more accurate and lighter than anything available 40 years ago when I started shooting and reloading for magnum centerfire.
I like them both, but I would get the CZ. It's more old fashioned, like me.