I found all the existing "big" spool holder designs to use too much filament have some other design flaws which I wasn't happy with, but I loved the spool holder that came with my printer for the smaller reels.
This design is basically identical to the standard one, but extended about another 30mm to allow for 1kg spools to fit. Still has the little lump to hold smaller reels adequately.
Note: The photographed version above doesnt include the little lump for smaller reels. I added it as an afterthought and didn't want to re print.