'cac-s' I only did a quick search & found 3 views on the Queen donks but using them & the many pixs of both types it appears that both engine versions shared a common thrust line, slightly above the wings chord line.. I'd be surprised if the thrust lines where widely different anyway. I used to fly the DH-104 (Dove) Riley 400 gee gee's version & often looked closely at the Gypsy/Queen version & they looked about the same to me. They flew well but where typical pommy rubbish, ergonomic nightmare!
Good luck & if yr building a model of one & want the exact thrust line then you are certifiable buddy
Wmk2