Need some input on fortifying ports in my mod

[PanzerMike]

Hi everybody. I am making my mod "Scorched Earth" and I would welcome some input from you guys.

Please have a look here:
fb.asp?m=4778429

The Vanilla 1939 scenario has recently improved the Atlantic wall events for the AI (it builds some 9 coastal defenses now). Of course human players can build any number of coastal defenses. What you CAN'T do is fortify a port hex, because the game does not allow you to deploy a coastal defense on top of a port.

I came up with a workaround for that. Now you CAN choose to beef up your Atlantic Wall by fortifying ports. As my solution stands now, the cost of fortifying a port is 60PP (ie one German division) and 1MP (just like a vanilla coastal defense sets you back 1 MP). The logistics (10 points) are returned to the pool, so no cost there. For that a port receives a 50% defense bonus (a coastal defense unit gives you 20% and only from attacks from a beach hex).

Is that a good balance (cost versus defense bonus)? What do you think?

PS This mechanism is only used by a human player, the AI does not need it (you can easily give the AI fortified ports by event using scripts, just like it is now for the regular coastal defenses).