What is a good all around foothold trap size for trapping otter? Is a ta-85 too big? Will a canine trap with offset jaws still hold one ?

Any beaver trap. Answer is easy for me. In PA only allowed one. So it's #4DLS

I've caught them in #2 Bridger 4 coil with no prob. A #3 4coil might be a little better. But either way they make good Yote and cat traps too. The 2&3 Bridger dogless are a good bang for your buck. They are base plated center swiveled and you can buy them laminated.

PS you can set them with 2 feet and 1 hand. Just stand on the springs, move the off jaw toward trigger side, push the other one down with your fingers and lift the pan with your thumb. No chance of getting snapped. All with one hand.

A 11/2 duke with a tight pan works very well . Offsets are not good . Ts 85s have rounded jaw faces that allow things to slip out of them IMO .
If the traps are staked I like smaller traps if they are on drowner I often set bigger traps .

My all around foot hold trap is a SLEEPY CREEL #3DLS OS

#14 jump for water sets.

I would not use offset jaws for otter.

I have started to over stake any BG trap set out 155 or bigger. They get into everything I set bigger than 110 now(even colonies). Even get mature ones stone dead in single spring 5x5's set for mink/mrats. Actually get the most struggle in 330's if they don't get suitcased.

#3 -correct size foothold for otters.

Some how I must have got an otter in one of my colony traps on a small stream, now I have several pieces of wire and clips. Ours can only be 6 by 6 and mine are all 24 inches but it sure got destroyed.

Bryce