As I suspected
After >12h of chugging away, only 7 of 36 maps made it onto the sd card in a way that rendered them visible. The maps that exceeded either the segment number limit, or the MB limit were split into separate parts, god knows how -- totally useless.
Conclusion: DIY. Roll your own compiled maps, load them onto an SD card inserted into your computer, or an attached ipod, then rename them, and copy them onto the microSD that you will insert into your handheld. This is for the "modern" units. For the legacy 60/76's, compile your maps into a single gmapsupp.img file, and copy it using the finder onto your microsd. Do NOT let MapInstall 4.0 interface with your GPS internal memory or directly with a SD card inserted in your unit until the software has sufficiently matured.
I'm sorry, this is not the bullet-proof, error-free, redundant software that I will depend on with my life when traveling the outback. It is a flakey, buggy, immature, not-yet-ready for prime time A-for-effort package that I am reluctant to use in any kind of mission-critical setting.
"I came into this game for the action, the excitement; go anywhere, travel light... get in, get out... wherever there's trouble, a man alone... Now they got the whole country sectioned off; you can't make a move without a form." --Robert De Niro as Archibald 'Harry' Tuttle in Brazil, 1985. The Mobius Trip index | Spot tracking live 4/18-5/4/13 | AdventureLoft™ Tent Space