In reply to all of your questions:
Whitehat:
Thanks. The width of the lower prong is not altered from the original dimensions of the wiper blade spine. There are 2 widths of spine that I know of and, as Pyro pointed out. My stock is all of the same width, which is a touch over 2mm on a normal wooden rule, but without my calipers/micrometer, I can't give an accurate figure. I think they are made from the slimmest spines though.
CitySpider:
Thanks. I haven't really had chance to try them out yet, as I'm spending more time here than picking, but with Good Friday free for picking practice, I'll let you know soon.
Pyro1234321:
Thanks. The diamond at the end is to avoid over-stressing the material. This material
will break if bent 180 degrees without using heat. I didn't fancy taking longer to make them by using heat, and the diamond at the end serves to allow you to keep them on a keyring, if you wish.
i_want_to_pick:
Thanks. Try making some, if you find an improvement on them, please post it.
Salzi684:
Thanks. They're not hard to make, just need a pair of pliers and a tiny bit of patience.
Technik:
Thanks. I didn't heat the metal before bending, not much point really and I didn't want to spend a great deal of time. This material will stand a cold bend to 90 degrees without any problems. Bending cold to 180 degrees will result in snapping the material though. As stated to Pyro, the 90 degree diamond shape will allow you to put these wrenches on a keyring.
To make these, and most other tension wrenches from this material, you can just use your hands, a pair of pliers and a little patience. Heat shrink also makes for a comfortable handle, but does lessen the feedback slightly.
Joecool2727:
Thanks. I haven't really tried them yet, but if it works for John Falle, I'm sure going to give it a try. CitySpider answered someone else's query on this with a statement that sometimes feedback is better than space. I'm a strict believer in this - the better fit you can make a tool which is inserted into the keyway, the more this tool becomes an extension of the plug. If you have a sloppy-fitting tool, you lose some of the feeling which is returned to you (sorry, this sounds dirty when I reread it

) via small movements between the plug and the tension wrench. If you can eliminate this, you will gain a more precise gauge upon what is happening inside the lock.