What are the 2 small compartments under the v-berth in the cabin for?
They're too small to store much more than a towel and they are a pain to access.
Thought they might be for ballast but that's just a guess.

I have three compartments in mine. Not sure why the 29 would just have 2? I removed the v birth mattress pad as we never sleep on the boat. That way the compartments are easier to access and gives more room. Also I attached cooler straps to store my cooler up there and it wouldn't get shook around. I can fit my 25 and 45 yeti up there. One of my compartments is sealed, the other two are not and have drain holes, stringers etc. if I store anything in those two I just use an inexpensive dry bag from wal market.

My 32 has 3 large ones there. Store all the stuff I never use there. That's were I keep my life jackets and seat cushions. The center one is large enough for an AC unit. I think my 27 just had 2 compartments.

my 27 has 3 compartments.my older 10meter has only 2.

I thought those were for extra beer???

They were put there for Reggie to keep his chains in when he was working on the boat.

What are they for? Effective use of space. Many if not most boats have storage under there. My 38 has 5 compartments. We used them for storage of floaties and other occasionally used items. It's is a pain to access with the giant mattress over it, so we only use the three that are close to the front.

One emergency and you'll wish you kept your lofe vests in a more accessible area.

Naw. In an emergency won't matter if they are sitting on the floor. They are only good if they are worn, and I'm ok with that choice

We only keep our extra (orange) PFD's in there - for just in case situations. Our regular PFD are readily handy for anyone on the boat.

Those storage areas are primarily used for cases of bottled water, cleaning supplies, etc. Like said before, things you rarely need easy access to.