Regarding "proper" hood(s) for the Elmar 90...
I would love to have a FIKUS ( the telescoping convertible Leitz hood), but I haven't found an affordable one yet.
In the meantime, I (mistakenly) purchased an IUFOO, for the 1950's & later lenses the have a groove on the front mount. It sort of stays-on with my 1951 Hektor 135, but could easily be knocked/blown-off.
This fall, I bought a cast hood from "Heavystar" for $9.95, which has an E-39 thread, and I screw that to the Leitz A-36 to E-39 filter adapter. This allows me to use the inexpensive hood on all my 90 & 135 mm lenses.
I also use the filter adapter to allow me to mount the "Summicron" barndoor hood on my 50 mm Summars & Elmar.
I took some shots in early December with my early '50s LTM Elmar 90, and am quite pleased with it... haven't tried any portaiture yet...
I think the only long-running issue with the Elmar 90 as a portrait lens is its slow speed... if you're trying to shoot portraiture in lowlight, hand-held, then Summarex 85 is more useful (and expensive! ).
I'm keeping my eyes open for a Thambar....
Luddite Frank