I have been running old and new engines of these types on this fuel mix with very good success.
25% castor, 3% Klotz, 15% nitro, balance methanol. This was reccommended by Larry Foster for his reworked Foxes and I have been using it to good effect on all of these bushed antiques. The K&B Torp 45 and 29R, McCoy 19, 29 RR Red Head and 35, and Fox 35 have been starting well, needle very easily and running very steadily and reliably in flight. The RR Red Head 29 I haven't actually flown yet, though as I have to build a nice Berkeley Swee' Pea B Team Racer for it.
Hope this helps with some of you guys old engines.
Chris...