Thanks guys. Working with flat metal from a tin tray was so much easier than the octagonal shape of the chocolate tin and having my tools back helped a lot. As the frame bag had to be hand sewn I went for the most basic design possible, ie, two bits of fabric the same shape sewn round the edges then turned inside out. It has a velcro closure along the top underneath the top tube, not ideal as access is very difficult with it on the bike. Stuff I need easy access to (waterproof/maps etc) will go in the backpack. I might put my water bladder in the frame bag to take weight off my back, I need to experiment with this.