I wholeheartedly agree that saya making is very close to rocket science. I couldn't even imagine the trouble of making one before considering to do so. I imagine that IF I try I will meet even more trouble. Even the Craft of the Japanese Swords covers the subject in about 10 pages with brief texts and dramatically few pictures. the thing gets even harder, if nobody has tried that before.
The difficulties mr Paul Martin posted at his post are just the tip of the iceberg. There are just too many points to consider. The 3 more improtant to me (for the point being) are how to mask the blade in order to avoid scratches, the habaki fit and the margin between the blade and saya). When starting the thread I was hoping for such pointers and a more experienced opinion on the risks. Naturally, experiencing on an iaito will be the first thing to do before ruining even the cheapest blade of my (mediocre anyway) collection.
I started this thread in order to make sure that it is indeed a good idea to try to do something like this at home, figure out the risks (learning the hard way is not an option with nihonto) and get some basic guidelines in order to understand the difficulties better. For more detailed questions, I think that the Japanese Sword Forum Sayashi subsection would be more appropriate as this is not a how-to forum. I really have learned a lot so far and I am sure I will learn even more until the topic dies and can't hold my self from sending my thanks to all those who shared (and will share hopefully) their mind with posts and messages.