Thank you so very much for all of this information. I am new to this forum and have found a wealth of knowledge here! I mentioned perhaps trading the blades (brand new in packaging, still have that sticky/wax on the blades) but the shop owner acted like that was a big NO.* Here's one of my previous posts that will give you some background info:
* That said, since you already have the 9.5" blade, it's OK for you to use it as long as the mounting plates do not extend beyond the outsole (except at the front tip). And I agree that if you've been used to the 9.5" blade, then it makes sense to keep it. I did exactly that myself. My first pair of Jacksons called for a 10.75" blade, which was ~1/4" shorter than the outsole. When I bought my second pair of Jacksons, they had re-designed the boot with a shorter outsole. If I followed the 1/4" shorter guidance, I would have gone done to a 10.5" blade. But I decided to stick with 10.75".
Note: You said that the fitter checked the 9.5" blade against one model of Risport, and the mounting plates did not protrude. If I understand you correctly, you are still deciding on the make and model of boot, correct? Be aware that the outsole length will vary with the make and model, so you need to verify that the mounting plates do not protrude on the actual boot you finally decide on. If you do run into problems: Are your blades brand new (unsharpened) with original packaging? Perhaps a fitter will allow you to trade for a different size, if needed? Good Luck!
I will let you know how it goes and what I choose!