I have a couple of quick thoughts on the blockhead designs.
The ultra simple design, ala. the Lefty tie, will work and is effective. However, I like to add hackle for two reasons. The hackle it adds bulk to the whole process making a bit more commotion. And more importantly, the hackle can aid in suspension of the rear part of the hook. This is not a big deal when using a light wire hook, however as you tie my (or any other popper-type bodies) blockheads with heavier stainless hooks, the hackle will help ride the fly more horizontally and keep it from sinking down in the rear.
I also like the deer hair tail to extend at least one inch behind the hook to aid in flat flotation of the fly. A softer wing or tail material does not provide this level of support as material like marabou will stay wet and not dry with false casting as the squirrel hair will.
I've tested my Roadkill design with and without the supportive hackle and found the hackled fly to be superior. I use two hackle feathers with the height of the hackle fibers at or only slightly longer than the gap of the hook. As an added bonus, this double hackle will not cause the fly to spin and ruin your tippet, as we see too often with other hackle flies (the Stimulator comes to mine...). I believe this is partially due to the heavier 8 lb. test tippet (or greater) used for bass fishing. I also use these for baby tarpon and generally run at least a 20 lb. tippet for them.
I'll be interested on what you guys find out about these design variations this season!