General update- I took my longest trip yet with the pusher trailer this week. 353 miles total with a single quick charge and one L2 charge en route. Otherwise, it was all hillbilly-hybrid! There were two 145 mile highway legs and 63 in-town miles in-between, during which I was towing around the dormant pusher.
Pusher control is still binary- meaning it's either running at wide open throttle, or not... This is enough power from the salvaged 1600cc aircooled VW engine to average 65 mph on hilly interstate, using the electric drive to boost power up the hills, and scrubbing off speed with regen on the way down (though I also slowed to 60 mph uphill and sped to 70+ downhill). That is 'charge sustaining' mode, in which I maintained SOC within two bars over more than 100 miles.
In this charge sustaining mode, I once again hit 19.5 mpg. BUT, throwing in the around-town errands at my destination, the trip averaged 24 mpg overall. Not great, but a bit better than I could have expected with the family minivan.
Economically, I would've been better off with a borrowed pass to the West Coast Electric Highway, as I refuse to pay Aerovironment's $7.50/session DCFC fee for non-subscribers, and it was logistically very helpful to not spend almost four extra hours waiting on charging sessions... The approximate $32.32 I spent on gas and $10.10 I spent on EVSE come out to 12 cents per mile, which is a lot more than MR BEAN's long term average of 2.4 cents, but equals the fuel-only cost in our minivan.
SO in summary, no better-than-OEM hybrid mpg numbers or great financial savings to report, but enough to continue refining the pusher, perhaps with a tune-up and throttle control.
The maneuverability of an i towing a trailer is compromised ONLY by parking stalls, and that's not bad when the tongue length is tuned to allow a full 90 degree parking angle between car and trailer (especially for an i at charging stations). Otherwise it can still go anywhere.
*update* it attracted some interesting attention on the Chevy Volt facebook group, will try to post a link later from home....