If doing F/T make sure you're getting the prey hot enough. Don't cook it, don't boil it, don't make it too hold to handle but iit should absolutely feel noticeably warm to you.
That's the only 'trick' I have.
Well, besides telling you that prey that is too small (and 47 is tiny but I don't know whether he's a very, very new snake or underweight) will OFTEN go ignored.