I fly the Yak 9u a lot,and was interested in the compression issue.As far as I know the Yak 9u didn't enter service till middle or late '44,this aircraft had a cleaned up airframe similar to the earlier Yak 3,but according to my information was of of all metal stessed skin construction,it also had the more powerful Klimov 107 engine first used on the Yak 3.I don't know if the Yak 3 had compression problems,but it would explain the 9u flight model in aces high.
Just to add,I feel the flight model is very good in general in aces high,compared to some other sims and the staff at htc should be praised for their research and attention to detail.
As for the Yak 9T,I have no information.
I hope this helps.
p.s. the Dora is a fine aeroplane:aok