The trainer mentioned there were other types of 'harnesses' we may want to
try, but not to confuse him by trying too many different things in rapid
sucession. That seemed sensible to me.

Do be honest, with him being that size, I personally would just stick with a
nylon collar. As long as you're consistent with him, he should 'get it'. You
can go nuts trying all the different variations of collars and harnesses and
what not, but if you aren't consistent, he won't get it.

Dale