I'm a new RadMini Step-Thru 2 owner, and having read about the tub idea in several areas.. I purchased the largest tub I could, to be ready for my bike's arrival!
BUT...
I experienced the same issues you did. Hefting the bike into the bin was horrible. I get the chain, mechanics caught on the side repeatedly. Lifting hurt my back. Chain came off. That bike is H.E.A.V.Y.
After one really frustrating wrestling match with the bike and tub... I started just "riding" the bike up into the back of my Escape (with back seats folded down).
It's so much easier!!!
I fold the Rad handlebars down, remove the battery. Lift the front end of the bike onto the back of the Escape. "Walk" the second tire up. Lay the bike down with the chain facing up.
I brought the bin back to Lowe's and got my $$ back.
I wish I had the strength and agility to fold the bike, get it easily lifted in the tub, and get the tub in the back of my SUV without a struggle. It would certainly take up less room than putting it in "full size" with just the handlebars folded. But I just couldn't do it. Maybe I need to go to the gym more-??
Good luck with your bike! I'm 89 miles in and LOVING it so far!
Jen