Today I managed to hit every light green, every traffic crossing or turn clear, so I didn't have to stop but a couple times each way (where there are actual stop signs), so wh/mile was only 61 average (vs 70+ previously).
Still high but shows that the real loss is from acceleration not from drag/rolling resistance (though I'm sure there is some of that, too, with the open-framework trailer/crate being so low to the ground it's not as much as the trike itself by any means, I'm sure).
Another improvement I'd like to get done tomorrow if I can is to add a handle to the top of the front "jack" wheel support. Presently I've been using my cane, handle-end partly inserted into it's top, to lean on and drag it thru the store, but it's hard cuz I have to bend over at a weird angle to do it, and keep hitting my ankles with the frame edges, and I don't have the cane to support me otherwise, so it's only with the rolling (and wiggling, with Yogi) trailer itself that I can support myself.
Should be easy to do, just have to measure, cut, and spotweld a small upside-down "L", with the taller portion of square tubing that inserts into the jack support, and the shorter piece of round tubing to make a good handle to pull or push it by. Might make it a "T" instead, with the crossbar of round tubing. Then I can make two "pushbuttons", at right angles to each other, that let it latch into the jack support in either of two ways depending on how i need the handle to fit to pull/push the trailer around and which side I have to pull/push it from.
Another thing I'd like to do is add a couple of small motors; they don't have to be fast, just have a lot of torque. Can be on/off, no speed control needed as I can gear them to be the right speed for crawling along, just pushbuttoning whenever I need the boost to push it along without the trike, on the smooth level floor inside the store, with Yogi in the crate and me sitting on the front "running board" basically steering with my feet along the ground.
Interestingly, I may have exactly what's needed, for free, in a "monster trax suv" toy car for kids to ride in, tossed out in the alley by someone in the neighborhood after the kids broke off plastics and switches needed to operate it. (pics later when I get them; it's too dark outside now and it's black palstic).
The SLA battery (7ah, 12v) appears to still be good, was 12.5v when I pulled it, and charged up with the Pb mode of the Accucel6 charger just fine, about 4.5Ah back into it. Havent' tested discharge yet, am still letting it just sit overnight to see how it holds a charge.
All it has for controls is a switch in a pedal, with an autoresetting thermal protection in series with that, in the Battery+ line. Then there's a switch for forward/reverse, whcih is broken off at the "gearshift" plastics, but the switch is probably still functional. Then there's an on/off switch for the main power, and a DC charging jack.
The power from all that goes to a pair of tiny brushed motors that run gearboxes that then drive the rear two hollow plastic 6"-ish diameter wheels. (the front wheels are identical but unpowered).
I haven't tested the actual thing as a whole, as it's too small to directly use as-is for anything I could use a small powered platform for--I'd have to stretch it out just to sit in it myself, or else all my weight would be way out over past the rear wheels, and I'd jsut wheelie up and fall on my back.
But I might relocate the powered stuff (with actual tires/wheels) to something more substantial as a "garden cart" sort of thing, if the motors can't be used to do what I want on this trailer.