Every airframe/powerplant combination has an 'ideal' Alt, going higher doesn't mean better overall. As an EG and I know it's not light A/C but the principle applies my last jet I drove before I retired had a service ceiling 51K', only ever got to 49K' as the TAS dropped off way too much and the time to climb was a negative. Most of our general GA hacks seem to be best at around 8.5K' higher than that means too much time to worry about not crashing after an eng fail??