Step 5: TRYING TO OUT-CLEVER THE SWISS
Initially I thought that I could do this by enlarging the blade and putting a thumb-hole in it (see Victorinox's own one-hand openers for what I mean) - you can see the intention in the initial blade-making pictures. However, when I actually tried to use it the hole was not really in the right place and it was harder to open than it was before!
My next attempt was to remove the metal bearing the hole and put a small stud in the blade for thumb-opening (like on the CRKT M16 knife) - all went well until I suddenly realised why this won't work on a SAK - the thumb stud obstructs the opening of the adjacent blades!!! DOH.
So I ground it all off and so now my blade is the same basic shape as the original. I left the back of the blade quite rough and with sharp 90 degree un-smoothed edges (where I had ground off the thumb hole and thumb stud experiments) as this will provide a striker surface for firesteels.
Serves me right for trying to out-clever the Swiss.