Ive got an Ikea sink and vanity combo that comes with a 1-1/2" drain line and p trap. Unfortunately, I realized today that I have a 1-1/4" galvanized drain line coming from the wall. Because there is very little space behind the drawers in the vanity, I can't put a fitting on the galvanized pipe to increase the size to 1-1/2. It seems that my only real option is to find a way to reduce the 1-1/2 down pipe/tail pipe, to the 1-1/4 p trap. Is there a product for reducing the size of the down pipe? If not, is there any reason I couldn't just use a rubber coupling with stainless steel clamps to connect the two?