IO, your post is not complete. If you mention PocketFMS, you should also mention SkyDemon (
SkyDemon Plan, flight planning software for desktop PCs) which has more or less the same capabilities but is a far more recent product.
What would be very nice if either PocketFMS or SkyDemon would allow you to import your own maps & calibrate them, OziExplorer style, and then use this as the basemap on which all airspace features are drawn. (Or not, at your option.)
That way you would be able to get hold of said "Underground" maps and import them into PocketFMS or SkyDemon, to get your route overlaid on a map with familiar color coding etc., but you also get the intelligence of a program that understands airspace, can warn for imminent CAS busts, knows how to handle TAFs, METARs, NOTAMs, fuel flow, alternates and so forth.