Minimum Width for Escape Proof Tank Rim

[jewett]

I have an old Pemco tank that I have never found an escape proof, tight fitting lid for so I decided to make some rims out of material I already have around the house. The front and back ledges will be 4 inches wide, but the "ends" will be just 2.5 inches wide. The Preventing Escapes article mentions using duct tape in a pinch, and my duct tape is only 2 inches wide so that made me feel a little more confident but I wanted to know if anyone has experienced escapes because ledges/rims were too narrow - and what the dimensions of those ledges/rims were.
I have made ledges before but the finished product was 4 inches on all sides (I think the 4 inch wide glass that I have been using for the current project must be left over from that project).
Thanks for any comments and tips,
Heather

 

[Jennewt]

My hunch is that 2.5 inches should be more than wide enough. I have not had any escapes using 2-inch duct tape (making a rim of about 1.5 inches when stuck on).

 

[jewett]

Thank you - that is a bit of a relief.
Heather