Dave's right. I've welded loops into just about every kind of line I own. The worst is the clear intermediate lines. It took four tries for the 8wt version to get that one to hold. Kept melting the line. In the warmer months I prefer to use 40 pound Big Game running line connected to heads with welded loops. One of the great things about this is when you break a running line on an integrated line, you just cut the head off and weld a loop in it. Bam you've got a shooting head that even casts better (IMO) with the mono running line.
As an aside, many of us who love the mono running lines also hate snake guides. Pulling any kind of knot through a snake guide can be a PITA. It's hardly noticeable with a ring guide. Another reason why manufactures need to build rods for those of us who prefer shooting heads.
Last night in my attempt to weld a loop in the leader end of an 8wt I line I finally gave up and ended up just making a extra long braided mono loop connector. Connected that and insured it with pliobond and an 8# blood knot at the end of the braid. A Lefty Video turned me on to Pliobond and I've been a fan since.