A little further progress ...
Mock-up of heftier frame with new truck side frame underway ... will make some refinements and/or further detail (like bolster end detail) ... then, hopefully cast a full set of these.
With some effort to organize the thoughts.
a) I really like the look of the skirted chassis and think something like that would work really well with a suitable 6-wheel chassis.
b) Was all set to "disregard" Prof K's compelling arguments for retaining the twin-bogie appearance in favor of the bulkier skirted appearance.
c) Cut out skirt and removed truck-cover panels to be installed separately for extra detail ...
d) Experienced the "Random X" factor that John New described here:
e) Held the skirt with openings over the chassis and finally "glimpsed"
a way to make the frame bulkier and build up the truck frames without too much effort. (And, when attempting to re-rail the loco with mock-up skirts in place, found that exceptionally difficult!)
f) Tried a variety of frame bits and kitbashed the truck frame shown above ... needs some bolster detail and maybe other refinements ... but likely I can get something going from here. (The Bachmann On30 passenger truck was a "near" candidate too -- w/b is almost the same)
g) See, that really was painful and long winded!
-- Thanks again to everyone for the various feedback ... no doubt more will be asked along the way!
-- Gerry & Gerald: thanks for the notes/thoughts on cab heights for various projects ... sure myself and others will revisit this subject often while planning other projects.
-- Martin: expect to have all the various doors, panels and/or hatches set slightly ajar, askew, unhinged, etc to add some depth ... without having anything that would show the "electrical gizzards" of the actual HO chassis!
-- Prof K: Thanks for the compelling "arguments" in favor of the twin-bogie design!