My thoughts also
Mark, thanks for posting this, that is the same aluminium angle I purchased this past weekend to see if I could build a sled for my router with it. I like a lot of the features you have incorporated especially the fine adjustment.
If you have used it much have you found any flexing of the aluminum angle stock? That was really my only real concern.
My intial thoughts were to make this with 2 small clamps of some type to lock my router in one position, one one each side of the guides. Then just use the sled handles to move the whole sled but leave it possible to slide the router in the guides to give me more that option.
I just havent worked out how to keep the lower clamp parts low profile so that if I don't have much clearence I can still get low the on project without interference. Will repost when I do, others thoughts are welcome.