Hi, I have 100 year old oak windows and frames, they are in generally good nick but starting to let draughts through in places. I have tried the stick on draught excluders but the gaps are not uniform around the frames so they don't work/fit well. Looking around the AQ21 range looks good as it sits within a groove and pushes out into any gaps. The issue is that I need to create the right channel for them to fit in, a deeper 3mm gap within a shallow 11mm gap. As these windows are in place it's impossible to get a router into position, either with a custom bit or using a couple of standard bits. Has anyone had any experience of retrofitting these and/or got any other ideas on draught proofing the windows. One thought I had was to install them into the casements themselves rather than the frame, would this cause any other issues?