|Mort the Cleverly Named|
Probably nothing worse than one would expect. Encounters will be too tough, advancement might be a bit wonky, that sort of thing. You can either adapt everything as is, or just have a pirate or two always accompany the PCs to fill out the numbers. That might be the best, simply because you won't have to change much and it will give an even greater opportunity to bring the NPCs into the story.
I'm playing in a two-player game of RotRL with gestalted characters and we've been doing fantastic. Skull & shackles is a different beast, though, so it's hard to say. I think a lot comes down to how smart they play it...you really have a significantly decreased range of acceptable error whenever one person falling into negatives can lead straight onto a TPK.
There are so many NPCs outlined in the first adventure that the party is specifically supposed to ally with, that it seems like Skull & Shackles might be one of the better APs for a small party, all told.
As I suggested in the Carrion Crown area, having a NPC who can follow them around filling in a needed role can help. They wouldn't be created to overshadow the characters and wouldn't be very talkitive, but can help a lot. Examples:
Fighter: Guardsman Otto signed up with the pcs due to the goblins raids and will keep working for a share. Chainmail,shield, longsword and bow isn't very flshy but dependable.
Cleric: Brother Harold is an acolyte who worked at the church that had that undead problem. Isn't much for wading into combat with his mace, but is a very good healer.
And if it seems they have too little manpower, maybe I'll have a couple of the many plot-related NPCs join their group.
This would be my first choice if I were GM-ing an understrength party in this AP.
Thanks for the responses! I might try Gestalt characters, it sounds pretty interesting and would fix the problem of having too few PC roles present in the party. And if it seems they have too little manpower, maybe I'll have a couple of the many plot-related NPCs join their group.
one problem it could cause: