Yea that is about right..Im no expert but from what Ive read,the max rpms are reached before the butterfly is fully opened..It takes some work to get a fully linear throttle curve but you can get close with a 5 point throttle mix..or dialing in some expo..I try to set my throttle so that the butterfly is 1/2 open with the stick on my tx at 1/2 throttle..doing this, the servo arm winds up pretty close to 90 degrees..then I can adjust my curve accordingly..

Im sure you will get some better advice from the more experienced but that works for me.