You can make this work out fine
Hi Todd,
First thing is to get good transition training so that you flying the airplane is not a source of stress/workload.
That leaves just the new airplane functional unkowns (mechanical and electrical) and the demands of engine break-in.
Of course do your best to handle all known squawks before first flight. Some people will fly with some known non-flight-critical squawks, but again, anything that adds to your workload or stress level is bad, so try to get everything working. Most important, all the engine monitor stuff should be checked out working. CHT and EGT info is going to tell you a lot that you need to know to be sure you are not hurting anything.
For first flight, everyone probably has diffferent ideas, but here's what I did:
Take off and turn cross wind and downwind while still at climb power. Right after take off, do a quick mental assessment of the airplane - controls function normal, trimmed, no strange vibrations, etc. Trim for climb. Make sure you are getting full rpm and manifold pressure, and most important, high fuel flow.
On downwind, assess engine - if CHTs and EGTs and fuel flow are all as expected, keep climbing. If anything looks anomolous, pull the power and land. As you keep climbing, orbit the field and keep monitoring temps and pressures, etc. Level at something like 3500 ft and set up a high-power break-in condition. Everyone seems to have different ideas. I just wanted to keep high manifold pressure and vary the rpm at several different settings in the range of 2400 and 2600, not staying at any one rpm too long, but keeping the power high. I did this for about an hour, just orbiting the airport within gliding range. Then I reduced power and landed.
I pulled the cowl, checked EVERYTHING, put it back together and went up and did it again for another hour. At that point, I think a substantial portion of the break-in is done. For the next three hrs of flight time, I started doing some flight testing, all the high-power, high-speed stuff like cruise engine temperatures, timing time to climb at different speeds, power-on stalls, and did a lot of avionics checkout while just burning up a lot of sky. Then, after 5 hrs, I think the engine was basically broken in. My oil consumption dropped some, but it was never very high to begin with, and CHT's and oil temp dropped some. I started mixing in some of the lower power stuff. By 10 hrs, it was really obvious that everything had stabilized, and from then on, I just treated the engine as if it was fully broken in. My oil consumption is 1 qt in 15-17 hrs.
I think the key info for your question here is to select the portions of the performance flight testing that can be done while maintaining high power settings. Of course you are always assessing that everything is safe to fly at all times. We all have the benefit that the airframe character is a known quantity as long as it is built right. So many of the 'envelop expansion' notions of slowly expanding and exploring handling qualities and controlability don't really apply like they would on an unkown airplane.
I'm sure you'll get a lot of other ideas here too. But I did not find it overly difficult to test-fly a new airplane and maintain high power settings for for break-in at the same time.