Do you've any pictures of when the bike was loaded with luggage?
The only problem I found using the 30 and 2 20 set up was when they were all full it was a bit of a pain getting the straps that attach it all to the bike nice and tight. Although I was trying to throw it all on as one block, I'd probably have found it easier if I'd hooked it all together on the bike.
Yeah I'll probably put the 30 on first, get that strapped down night and tight, then attach the 20s.