Not if you tether the float pouch to it. I tested by tossing the PLB1 with the float pouch tethered to it into the water. The float pouch stay afloat with the PLB1 hanging below it.
No argument as long as the pouch is treated as part of the PLB for this use. I was referring to @JohnnyC 's comment "You're going to want to peg the PLB to you anyway, so having built-in buoyancy is a non-starter" which implies to me that he would consider non-buoyant versions i.e. PLB1 with no pouch.
PLB size matters to me as I want to put it in my BCD pocket to steam line my gears. See the relative size of these 2 PLBs, below and image you add canisters to enclose them.
View attachment 537313
The 400/425 series is a little smaller than the older ResQLink+s and fits into an approx. 2-3/8"dia. x 2-5/8"- long (interior) cylinder with the (included, accessory) Velcro attachment strap on and likely room to fit a lanyard as well.
What interior dimensions did you finally come up with for your cylinder with the PLB1 & pouch?