Thanks, I thought the upgrade types were limited to types that came into service AFTER the start of the war (Gato and Balao).
I guess I've been 'unlucky' with upgrades and new commands, since I have renown up the yin-yang, after 4 patrols (middle of '42) I usually have about 10000 + renown (or does that make me look like a complete noob???

), I understand that amount of renown gained from sinking ships is related to difficulty? (I play at around 70% difficulty, manual TDC all the way

).
Is there an amount of renown which should always (or very likely) produce a new command offer or tower/sail upgrade?
Greetz,
@Lantis