Just remember not to do it if your state does not allow the possesion of larger mags (CA for one). Here in MD we can't buy bigger than 20 rd mags for any gun but we can go to another state and buy them and bring them back to use without violating the law (screwy law).
If you can own functional 32 rd mags then in the case of the Promags just screw them apart and remove the pin or block and put it back together. As long as it has a full sized mag spring you are good to go.