G'day Sigrun,
Where is it written that one must extract every last rev out of an engine, we run an OS 46AX, with an APC 12x6, & a Taipan green plug, my girlfriend flys it, in her Skyraider mk1, at half throttle, & even at full throttle it is still very controllable, the motor don't care, it is always a first flick, against compression start, & runs sweet.
Come to our field sometime & we'll show ya.
Here it is at Armidale last year, that is her plane at the home page, & we are not even members,
http://nemac.com.au/