Hi Chris,
If you can hook up with Dana for a lesson do so. It will most likely advance you down the learning curve 3-5 years. Nothing beats a lesson from a good instructor.
But if you can't or just in the mean time I will walk you trough a simple exercise to put all of the above brilliant information to work.
I am not sure if all of you spey casting is actually fishing or if you do some practicing on the side. If you just go fishing (super cool and I wish that all of my time with a two hander was actually chasing fish) you will need to set aside 30 min. or so fish to run through the exercise.
Choose you cast that you want to work on but I am going to walk you through a single spey but you can do this with any cast.
1. WATCH THE ROD TIP through the entire cast. This is easier said then done sometimes but you will learn what is going on quicker this way.
2. pick out your target. A land mark across the stream.
3. watching the rod tip, start you single spey, nice and smooth, and fire you back cast and STOP. Just let the belly/d-loop fall to the water. Do not fire your forward cast yet (we don't want to rebuild the second story of the house before we make sure the first level is structurally sound). We will work on the forward stroke in a bit.
4. Now look and see where your fallen back cast is pointed. If it is 180 degrees from your target, directly opposite, then you are in good shape. If your fallen d-loop is not pointing opposite your target then lets work on it some more before going on to the forward cast.
5. Now look at your target across the stream and then look behind you and up to 1:00 over your shoulder and look for another land mark that is opposite you target. Like the top of a pine tree or something.
6, Now repeat step #3 this time watch your rod tip go back and fire the back cast and aim at your back cast target. Hold the rod at 1:00 agian and let the d-loop fall to the water. Now look at the belly and make sure it is pointing opposite your target. Roll cast back down stream and repeat for a while to get the feeling and consistency. No forward casts until you have it pretty consistent. While working on this you should be paying attention to the anchor or grip to make sure it is nice and consistent as well.
Now the back cast is consistently opposite your target and your anchor/grip looks good.
7. Now, while still watching the rod tip every step of the way lets fire a forward cast at your target. Everything should be lined up and on the 180 degree plane. Now if you just fired a tight loop and all went well, very good, if not, we will work on the common stuff.
8. This time make your cast and watch the rod all of the way through. Here is what you are looking for...you have come back a formed a perfect back cast and as you pause to form this back cast, you make sure, by watching the rod tip, that the rod stays pinned at 1:00. It is very common to have the rod drift forward at this point. If the rod drifts forward to say high noon then you have nowhere to go on your forward stroke but either 1. down super low on the forward stroke resulting in a huge open loop or 2. you force the rod to stop high but to do so you had to make a very quick abrupt stroke that will end with a tailing loop.
9. either way lets fix it. Now make your single spey, watching the rod tip all of the way. As you form the back cast, stare at the rod tip and dare it to prematurely drift. Give it the skunk eye if it even thinks about it. Nice, it has stayed put and you have a long stroke to look forward to. The back cast has grown into it's pointed > shape and it is time to ease forward. Start the stroke nice and easy, still watching the rod tip, picking up momentum as you go, and at the last second apply a short but stoat pull with the bottom hand and stop the rod high to fire the cast.
If you work through this it should help with the 180 degree principle and a nice, smooth forward stroke. Most likely eliminating any tailing loops or line collisions. If you can get a lesson,do it for sure, if not, watching the rod tip through the entire cast might help solve problems and smooth things out.
I hope this helps,
Greg