Purchased 2 units for our entrance bedrooms as we have been on a noisy main street. Put in them yesterday and the difference in noise is awesome. I went for your 6.4mm laminated glass and positioned the units over the entrance with the window sill to present maximum hole. https://secondary-glazing-for-noi77009.link4blogs.com/55852608/indicators-on-london-secondary-glazing-you-should-know