This is an interesting thread - and I would agree with what has been said above.
I grow all my multiflorals in the brightest part of the north facing shade-house (Southern hemisphere) and they are bathed in full sun all day. Even through the shade cloth is at 70%, in summer you still bake when standing on this side of the shade-house. If I hold my hand about 1m above the plants, the shadow that my fingers cast is still distinct. In addition, I also feed weekly-weakly all year round and they have nearly all rewarded me with mulitiple growths.
What I do find with high light intensity is the dramatic effect on the leaves. Certain species (gigantifolium, stonei and sanderianum, in particular) and their hybrids grow new leaves that are generally about a 1/3 shorter than the older leaves when I received my plant. My Paph. Mem. Joan Levy arrived with 4 leaves well over 60cm long. All new leaves on the original growth and the multiple new side growths are at a maximum of 30cm long - but they are much broader than the original leaves. It does give the plant an odd grafted-cactus look. On the plus side, they're much easier to handle and don't take up so much space on the bench. Has anybody else noticed such a dramatic effects on the leaf length?
Kind regards
JL