Lucky,  I have been thinking in terms of some of the flies some guides and I worked on for driftboats on trout rivers. We found incorporating rubber legs (like sili-legs which have great movement) in a helical pattern into estaz or chenille both provided movement and  illusion of size (profile). Kind of like an ultra wooly bugger.
Another thing to experiment with. For now, I need to get some steel on the bank with nice, easy eggs and nymphs.  Hope I run into you, Dime. I'll be camping  at Stoney's.

The most effective helgdamute pattern I ever used had rubber legs and a foam head pulled forward and tied off... olive chenile or brown body... think it was calmed the Delaware river helgramite. Tied with weight on the hook. Usually dead drifted followed by a swing out in the end

i have a very affective helgramite pattern...one of the guys at the BP fly shop came up with it a couple years ago....closest thing to real i've seen and not hard to tie

Got a pic or a link, bear?  I met some guy using Dobbies (what some call them, as they are Dobson Fly larvae)  and doing well in Pineville on steel last Dec.  I generally  just use a long tail of marabou and ostrich herl with a dumbell eyed head and rubber legs. Always interested in what may work better, though.

Fichy, I can't do the link thingy, but check out Floyd franks Delaware river hellgramite pattern... we used to fish it for trout In the Delaware system and do well back in early 90's. If you could post the link that would be cool. We didn't get as intricate as the true pattern did but close enough and it worked great. The long shank streamer hook bent upwards by the eye of the hook gives it a nice twitching action i'd suppose... if I could only shake this 5-9 working schedule i'd be tying away at my vise. My son has tied more flies than me in the last few months... "all of which are american dreams"... or so they say ;)

http://www.flyanglersonline.com/flytying/fotw/101199fotw.php
Dime-here's that pattern.
 

Thanks gerry... it really is an easy fly to tie and its highly effective. Gotta love the closing statement he concludes with... "if you're not ticking bottom you're not using enough weight"... and this is coming from a purist minded fly fisher... I love to tie flies that have a pull forward head or pulled back head/ body... couple that with hackle feathered beards, tails, or shucks... man that's fly fishing to me... used to fish natural nymph patterns on a straight tight line down stream above pockets for trout and have trout hammer them. Then fish the same patterns other times on a dead drift... Fly fishing to me is thinking out of the box. There's no rule. You can create you're own rhythm given the conditions presented to you. The text books can tell you the best case scenarios but they go right out the door in most cases... nothings perfect, or at least rarely perfect text book conditions.
I hope some of you folks tie this fly up and have success with it. As my family and I enjoyed much success in the north western cats and upper Delaware and its tribs.

no link and i can't post pics on here because i am a computer idiot, but if you want to pm me a number i'll text you a pic of one