If you're happy with the gauge you play now on 4 string, find a set for your 5er with the same gauge EADG. I have a 45-125 Dunlop set of nickels on my 5er, and it sounds pretty good. I have a 4 stringer with set of Curt Mangan stainless steels, and although I really like the sound I get, the tone does not go with the other instruments in our church band. I have found that the tone I get from nickels sounds much better in the mix. I plan to put a set of Curt Mangan nickels on my 5er when the Dunlops go flat. Main thing to know is that some 5 string sets have a somewhat floppy B string. You'll notice on balanced tension sets that the B string is significantly larger than on standard sets. Typical set of strings would be 45,65,85,105,125. Balanced tension set would be more like 45,60,80,105,145. You may want to check with Jason at BASSSTRINGSONLINE.COM. Let him know you are a talkbass member, we get discounts. He is the man when it comes to knowledge of bass strings. Let him know what you are looking for, odds are his suggestion will be just what you need.