Terry,
I use my #3 Smallstream every time I get my Epic 370 out, whether that is on a river or a loch. I love it from a float tube especially, when I can cast long (ish) or short and presentation is key. It usually only has one fly but recently on Loch Shandra I fished a Kate McLaren and a Bibio, both in #12 all day with great results.
To be honest, I pretty much use the Epic with that line for nearly everything these days!
Euan