Yes I agree! I always have to order a size up in my TB shoesI've found that Torrie Burch flats run small.
I wear a size 4 US and have bought Torrie Burch size 5 US...and they were TIGHT until broken in! Now they fit fine, but at first they were very, very uncomfortable.
I can't imagine actually wearing a size 5, ordering a TB size 5 and breaking them in. Ouch.
If you are a size 5 you might try on a size 6 and that might fit better in a TB.
But great idea to cut the elastic! It works and now you can wear the shoes!