Not on the claw style I don't see an issue. That is how mine is set up

So will the 4# be plenty for a 16 foot aluminum boat?

I also have the anchor that looks like a shovel. I believe the anchor comes from the Northern Sea. They use them to hold Oil Rigs down. This anchor will not slip and most of the time I only need about 20' of rope to hold the boat. I have a 21' bay champ and the anchor made for the boats up to 21' works perfect. I also have the shackle at the top and run the chain down the anchor and tie wrap to the bottom. So If It gets stuck you can pop the tie wrap. It is worth every penny.

Will these kind fit in my anchor locker? If not, any ideas for how/where to store it?

It fits in my Frontier locker.

If not, get a piece of PVC as long as the shank on the anchor and big enough for the shank to fit in and mount it that way.

I have an 11lb shovel anchor in my anchor box in my 24' NauticStar

Mine goes in anchor box also

Yes it is.