First of all thank you all sincerely for your help in my old post, but things were getting muddled and advice missed and conversations it was all counter productive by the end.
While I am again grateful, my query has changed and it was difficult to get that across there, hence new post.
I'm happy to delete the other post but will leave it up for the moment in case anyone needs to see it.
OK, so assuming the pictures load in the right order I've put my iaitos 'natural' sit held vertical in the saya. I think it's fine, I've never had it fall out, though I obviously always have one hand on it like I'm a bushi of old always expecting to be attacked. But at my last grading the sensei tipped everyone's saya upside down and if the sword fell out you were told you couldn't train/grade. I am now paranoid, as...
... unless I apply a little (it is a little) force (pic 2 is the result of said force) my sword does fall out (it wouldn't from pic 2). It doesn't slide straight out the second it's tilted, but it does once it is vertical.
Hence my sudden shimming quest.
The other images are my koiguchi close up, imo the wear is almost exclusively at the mune side, though the ha looks a little worn too (despite the pic the wear is fairly even at the ha; the pic to me makes it look like the upper right is worse, think it's the angle).
I guess all I want to know is should I even be shimming yet? If not for the grading i don't think I'd bother yet, but it'll be a long trip to the next one and to be refused to grade would be a huge problem.
Oh and the last pic is 5 of my veneers together, as I couldn't accurately show the thickness of one - a lot of people were telling me the shim was too thick, I would say they are about 0.6mm each?
Again, sincere apologies for making another post on this topic