I can't remember what the v. 4 is made of but I am thinking 2 things:
1. Wrong fit
2. Wrong kind of absorbency
1 could be a matter of adjusting it bigger or smaller. No reason to give up on the TBs yet.
2 find out what they are made of and depending on that I would ad either something that absorbs quicker or something that can hold a lot off pee
And do let us now how the testing is going