Being a Mepps Expert. Use the #5 on the med.hvy. or a bait caster. Use the #3 Mepps on the med. spinning rod. #3 mepps is way to lite for a baitcaster. #3 works very good on 6lb. test and the #5 on 10lb. test. I get away with 4lb. Fireline with the #3 mepps but i back off a bit on the cast and that baby gets out there 120 feet or more. I've lost a few on 4lb. SNAP PING gone.
I think you'll be better with the 6lb. test fireline or other 6lb. for #3's I send them with 6lb. fireline.
I use #2 mepps with 4lb fireline alot in shallower water.
# 4's are good with 6lb fireline or 8lb other line.
Hope this helps and please ask anything about Mepps seeing i have so many hours with that lure for sure
h2o<---says there's less than 300 Mepps Experts in the World
Greg I can throw a #3 on a Med Heavy it depends on the action of the rod. You fely yhe action of my Buck Tail Rod I think you know I can throw a #3 on that. I use a fast action for the lighter lures. You are right about the line weight it has to be light for the #3s. Greg give me a call I have something to tell you. Bob