I fly from a gliding club that uses lycoming engined Chipmunk as tugs so I am familiar with the conversion. They are not cleared for aeros so you have immediately lost one of the key essential elements of the Chippie.
Mark 1 - The RV-8 certainly looks like a realistic alternative to the Chippie, one question though, and that is around the undercarriage. It does appear to have a wide track but with those long legs coming out at an angle from the centre of the fuselage, do you find that it rocks from side to side whilst taxiing? The Chippie feels planted when manouvreing around farm strips where the surface is uneven, how does the RV-8 compare?
EDMJ - the Citabria Decathlon, Cub et. al do offer many characistics of the Chippie especially being seated on the centreline. However the high wing seems to me to be a hinderance to all round visability (although I must admit I have not flown in an aircraft of this type to actually know if this is true).
Shaggy Sheep Driver - I have never really understood why the Chippie is nicknamed the poor mans Spitfire. A wing with straight leading edge and deep wing section; fabric covered wings, rudder, and elevator; a wide track undercart; and that large framed sliding canopy always remind me of the Hawker Hurricane. Certainly each time I strap myself into mine thats the aeroplane that I make believe I am flying
!