It's been a while since I've done a build, but here's my latest. Excellent project to put together, and really adds to the immersion of the cockpit. I started with a straightforward build but ended up taking that apart and doing my usual sand/paint/weather job and added a few extra details.
Most of the ideas were from gaznav, especially the perspex sheet and the magnifying glass lens. I modified the 'patent' lettering from another user by warping it in Photoshop to fit better. The reflector glass (perspex) was held onto the mounts by a couple of small custom 3d parts which were screwed on. I also created a 3d rim/insert to hold the magnifying glass, and sprayed the underside of the glass with metalliser paint then black to give it a mirror finish.
I created more 3d parts for the 'head protector', plus 2 brackets for it that were bolted with holes drilled through the upper body of the gunsight. The head protector was covered in material from an old sock stuck on with PVA glue . A few fake rivets rounded off the look. Plenty of artistic license but it's a great addition to the Spitfire build.