I have a 7 PIN, Bottom line with a 19 degree transducer. I would like to make an insulated box for it and take it icefishing. Are there any certain numbers I need to look for? or ways of telling what 7 pin icefishing transducer will work with mine? I would like to buy 2, One 19 degree for shallow and a 12 degree for the deeper spots.Thank you for any help that you can give me.