I always put the heaviest beam lowest on the mast.
That of course is the best mechanical configuration but pattern modeling sometimes disagrees and has been brought up in print and on the Internet many times.
There was no way I was going to put a full size 4el 20M yagi with a 40' boom at the top!
Unlike TV antennas which have multiple resonances so are really a completely different subject, the 6 and 10M yagis do not share that problem.
Those 5-6 band ham yagis can become a problem since 6 and 12M will interact as will log periodics.
Im currently sharing an all HB array of 3el 20M, stacked 28 el 32' booms on 432MHz, and a 35' boom 8 el 6M in that order, bottom to top with about 11' of mast exposed with no apparent interaction....the observed patterns and performance are as modeled.
What did not work was when I tried a TH-6DXX about 7' above a 4el 40M KLM on a 42' boom. The TH6 was dead on all 3 bands when I tried it as a contest multiplier hunter; it was fine when tested by itself earlier. The KLM was unfazed.
Carl