6mm footbeds

I've fitted some 6mm Inov8 footbeds into the Ultra290s. Unfortunately they only sell them in full UK sizes despite selling the shoes in half sizes so I had to trim them with scissors. What's going on there? As might be expected the thick footbeds had the effect of lowering the heel cup by at least 3mm and making the shoes a little tighter which might be an issue in view of my high arches. At the weekend I'll see if this has been a good move.