i'll proceed by elimination
1st PK v50 + ~130 apps
if that works smoothly (as i expect it will) i'll try CSSU testing then, maybe?
should i install it 1st (i.e. after reflashing & before installing anything else) or last?
then i'll have to cut back to the bare minimum and add one by one, to see what might be causing issues.

[/off-topic, i guess ]

i hope you appreciate that's not something you can ask a casual user to do.
nor to install only a hand-full of 600 (or 700?)+ apps
whenever i get a chance i point out to potential users / buyers of N9(00) that those few hundreds apps provide all that's really needed, but if they can't even install (most of) that