Pop-rivet the brackets in place whilst the airframe is still inverted, and turn upright as here to admire your handiwork for a moment.
If you think this is not a secure means of fastening brackets, incidentally, try removing them if ever you've installed them upside down... as I have on occasion.
Our 'flying phone-box' is now ready for painting, which is the fun part or at least until you die from emphysema some years afterward.
If you're working in the cold (as we do all year in the UK) then bring in both the paint and the space-frame for a 'warm soak' prior to application, which generally requires a temperature of 15 degrees centigrade.
N.B. The only difference between Celsius and centigrade is the first is harder to spell.
