I’m having the same problem since the update. Sometimes even with full right rudder it’s not enough to stop it looping around. I’m pretty sure if the real Spitfire was this difficult the Battle of Britain (flown by many inexperienced guys just out of flying school) would have turned out very differently.
Edit: found this other thread (New Release : FlyingIron Simulations Spitfire L.F Mk IXc - #294 by Severeeno), and maybe the crosswinds are too strong. I will try to notice this next time. I often take off from Manston and there’s a frequent crosswind on runway 10/28 so maybe time to go unearth the old grass-strip!