RE: HK90mm viper mw44 conversion she Snaps!
I don't think it's going to be too heavy. (Assuming it's the 90mm version)
It sounds to me like you may be nose heavy, or that the main landing gear is too far back. (making rotation hard) Personally, I would double check the balance, and push it back a little if you can. Then... I would make the front leg a little longer, to bring the nose up.
Is your Wren the "Gold" version? If it is... 180K RPM's is only 7 Lbs of thrust. I would turn it up to 185K and see if it acceleration a little better. If it's the old version... I would run it up to full RPM. (195K)
Then finally... I would add a little reflex to the ailerons. Bring them up a couple degrees. And don't use flaps for take-off. (They may be pushing the nose down while in ground effect)