As to a clan, I'm not sure its really worth it. Outside of a chat channel that you automatically join there isn't anything else there that you can't do from a normal chat channel/friends list unless you have the numbers/tiers/skill to participate in clan wars.
As long as you make sure everyone in cuk is on your friends list/in a cuk chat channel then I don't think a clan is really worth the expense.
Also,
Here is a replay of me playing the SU-122-54 (agile Russian TD line)
I forgot the replay I sent in for a contest was featured in a roundup (not quite good enough) on Jingles' channel. It's a game where I got stupidly lucky, I should have died going after that E75 to the Jgpanther (pay no attention to him saying it is very well armored... angled yes but armored no, the only armor is the gun mantle - I just got lucky and somehow bounced his shot off my side...). Didn't even get my ace mastery badge from that game. (not that long after the tank came in so I can only assume godly players had inflated the xp needed in T10 games.) He doesn't mention that there was only 20 seconds left on the clock at the end!
If I had fired (and hit) the Tiger a second earlier and hadn't got stuck on that fence post preventing me from getting a shot on the Ferd I would have damaged every single tank on the enemy team.