On Tuesday, May 23, 2017 at 11:31:44 AM UTC-4, Sean Fidler wrote:
Arcus overheating: I understand that one cannot run at full power
for more than a few minutes with the ArcusM (or 32?).
Sorry if I'm mistaken.

You are mistaken; ArcusM (unlike 32) has no time-limit on max power.
Max RPM is limited to 5 minutes 6600-6700, but max power is 6600 anyway.
Range in the manual (with 3 tanks) is listed as 135nm.

As I understand it, the ArcusM and others like it are designed for
self launch over an airfield and immediate soaring, not cross
country cruising under power.

Yup. Absolutely not optimized for XC cruise under power.

The only downside I can see is that landouts in fields are not a good option
(flipping over forward in soft ground is a risk) and once in said field
getting out would be a major undertaking.

And field landings are prohibited in the manual IIRC.
So Stemme owners I know must be much more conservative about getting low.
As in any motorglider, landing is plan A. Plan B is when the motor starts.

I also wish to fly at an airport where the Arcus or 32 would be very
impractical (likely impossible). I would need to integrate with moderate
regional airport power traffic and there is no grass parallel for
glider operations.

I fly my ArcusM at a regional airport with plenty of power traffic.
No problem to assemble solo in the AM and taxi (to and from runway).
You've seen me taxi to runway and back to your hangar at your home field.
Its a different machine than Stemme, but perhaps not as limited as you imagine...