I only dimly recall the report on oversized dehus - it may possibly have been a footnote or sidebar in the 15-20 house dehu optimization study done in Houston and sporadically posted here. I just remember convincing language to the effect that dehu capacity has lately grown such that it way exceeds demand in a typical homeowner app, and that this serves no one other than bigger-is-better marketing twits.
I agree that the oversizing downside is not nearly as problematic as with AC, but it does mean overspending on, and putting up with a larger and heavier unit than needed. I also strongly suspect that the liters/ kWh efficiency numbers fall way off in intermittent conditions owing to startup and shutdown inefficiencies including but not limited to refrigerant pressure reequalization and condensate reevaporation from the evap coil. The Energystar savings is printed on the box but not really actually installed in the home.
Now that you mention it, I'm not sure I agree that dehu capacity can't reasonably be modeled via something like Manual J? Just off the top of my head why couldn't one run a Man J calc using reasonable numbers for infiltration and just look at the latent portion of the result?
OTOH, a portable dehu only costs $150-$250, so chuck one into the crawl space or basement, maybe along with a hygrometer and a Kill-a-Watt if you have above-average curiousity, monitor results and go from there - it's not like it's a multi-kilobuck ducted HVAC install...one can probably sell a fairly new one for half the purchase price so the risk is pretty low.
I'm cool with opposing posts, especially yours. I've mentioned here before that I'm an engineer who has wandered out of field - some of my posts here are trial balloons designed to draw comment. I've been whacked a couple times but learned something each time.