Fly Fishing with a Strike Indicator handing a balanced leech can be highly effective and it sure is exciting seeing that float go down, even more interesting watching the rainbow trout underwater.  Check out the action as these trout go crazy for leech pattern flies.  One a high vis hot pink and green attraction pattern and a natural black pattern.  Hope you like the video and my thoughts of what that float is doing and why.   
 

What would be the point of going slimmer if the fish are eating this one like crazy?  This video was taken last fall like around October/November.  Is that when you use blood worms?  I was catching fish pretty continuos as it was with what I was using then.  In the BC interior lakes we usually use what we call micro leeches.  We use shorter small hooks rather than longer hooks, tied on a #12 or #14 hook.   I know a slim body seems to be what a lot of guy talk about, but fat bodied leeches work great in the fall.

I don't think I fish with anyone really that I'd classify as elderly yet.  My Dad, my uncle and my father inlaw.  Also family friend Rob.  I think the oldest would be my father inlaw and I think he just turned 66.  He still runs his farm and fixes equipment and what not.  Didn't think of any of them as elderly yet.  I'll check out the link, thanks.  Good luck with the lead core.