Not wanting to complicate things, but I was playing with 7-Zip
a while back in conjunction with some add-on aircraft for another sim, and I was getting some astonishing compression rates.
I eventually concluded that this was partly due to having multiple skins for the same aircraft -- the "solid archive" option enables these to be compressed far more efficiently, as the skin files have many similarities to one another. But 7-Zip really does offer useful savings in general, and although I'm not sure what the details are of packaging SDOE add-ons these days, I figure it might be capable of keeping this package to a single CD.
With random data I find that you can expect to save around 20% over a zip simply through superior compression algorithms, but for flight sim mods I had one "Strike Fighters" aircraft that went a 17MB zip down to a 7.5MB(!) 7-zip file, so these seem to be an ideal application. WinRAR did not perform nearly as well.
The software is only 1MB to download. I find it easiest to right-click on files/folders in windows explorer and select the "Add to archive..." menu option.
If you experiment, make sure you use the "7z" format and the "LZMA" method (these are the defaults), and choose at least "Maximum" and maybe "Ultra" for your compression settings, and select "Solid Archive".
Self-extracting archives can also be created, of course. I'd say it's definitely worth a look, if you're not already using it!