I switched to a shooting head system on my 8 wt. last years on my fishing buddie's suggestion. He even made one up for me. The trouble is that I can't cast it for crap.
Is there a formula for head weights and lengths? Or do I just keep experimenting?

Trey Combs book on Steelheading has some of his formulas for sink tips and shooting heads. I can say that a sink tip on a fly rod feels like s#%&. Having said that, I have a 30' type VI shooting head on my 8wt that sinks like a rock, but will throw a hell of a lot of line. Experiment and practice!
You don't always have to single or double haul a sink tip, I find that I roll cast mine 70% of the time due to lack of room.
Good luck!

My single-handed sinktip steelhead consits of a 30' floating shooting head 2 line sizes larger then my rod cut back (from the tip) 8' feet. I then loop (monocore loop) the cut back floating head so that I may fish varying sinktips (13'-18' Type III-VIII) with the line.

The rearend of the floating head is spliced into .028 Rio Powerflex Core floating running line.

This system shoots a good 30'-40' with just one false cast to position the splice just outside of the tip-top.

When I really need extra distance, I strip the spilce right to the rod tip, then perform a Spey cast in which I dump the head in front of me, then (as long as I have a tight line) throw my backcast and let her fly on my forward cast. This waterload casts gives me extra distance with little effort (plus, I can cast upwards of 70-80' with out need for much room behind me).

If you are using a standard running line, you can use standard shooting heads that are the same line weight as your rod, or up to 2 or 3 over, depending on the rod. If you want to make your own with LC-13 or TC-14 use this to get the right length: http://www.flyfishingforum.com/expertise/knowledge/lineratings.htm.

It is also possible to overload a rod and achieve good results, like I fish a 9 wt Rainshadow XCEL rod with a 400gr shooting head.

Now, as far as casting them, the heavier they are the more you should try to strive for one backcast. If you are having trouble with getting the cast started, try bringing the shooting head in the rod a foot or two and letting it out on the false cast. Its a good idea to learn to double haul, as that will help your line speed.

Rob

How much of the head is past the tip of the rod? If you have several feet of mono backing past the rod tip, at some point it will not back cast very well.

Try keeping some of the head in the rod. As you gain experience, you will be able to have a few feet of mono past the tip. Also look at the loops you are holding. Make sure they are not clinging or twisting prior to the cast.

Giz...

Ryan, sounds like..

"When I really need extra distance, I strip the spilce right to the rod tip, then perform a Spey cast in which I dump the head in front of me, then (as long as I have a tight line) throw my backcast and let her fly on my forward cast. This waterload casts gives me extra distance with little effort (plus, I can cast upwards of 70-80' with out need for much room behind me)."

you're doing a "Perry Poke." One of the most effecient casts for pulling/positioning heavy heads for winter fishing. And, as you note, almost any spey cast can be done, and done well, with a one-hander rod.

Yep, yep. I have always hesitated refering to it as a Perry Poke because I actually use either a Snap-T or a Doublespey to position my anchor and never the movements that are true to a Perry Poke.

...but yes, like the Perry Poke, it is a waterloaded cast that is very efficient and very powerful!