So my problem was the piece of foamcore I put along the bottom to make it more rigid – take it out and the bag opens flat! I added some elastic to hold stuff in on one side and an organza piece on the second side (may take out the organza and replace it with elastic). Much easier to pack now.
The bag holds clothing for a week, plus my travel pillow easily, maybe even one bag of cosmetics.
So now, I’m sitting on hold with Air Canada to ask whether my folding luggage cart (which I still have from the days when luggage didn’t have its own wheels – you put it on the cart to move it along) will be accepted as carry on!
Difficult question, it seems – I’m on hold while the poor soul on the other end of the line checks with superiors about this one!
Answer: If the length of the cart is 21.5″ or less it’s OK. Now I have to go measure my cart!
jmn 
Interesting approach. would you consider buying four small rolling wheels and put them on a thin but strong board on bottom? Or pirate what you need off a piece at a used place?
The cart is cumbersome. We had them as well.
Sent from Andrea’s iPhone
All interesting ideas… will think about this some more.