Hi,
There are several CLC PS Forum posts from former PS builders relating to the use of expandable foam flotation. See for example:
viewtopic.php?f=3&t=405&p=1204&hilit=pocketship+build+space#p1204.
There may well be other posts in CLC's regular forum about using these products too. I also know several PS builders have discussed their use of expandable foam in their blogs, complete with photos of expanding foam!
I recall John Harris mentioning that the use of expandable foam can render access to the compartment interior for inspection or repair extremely difficult - although none of us want to ever have to access the bow compartment again, so one might discount this as an issue. I know a couple builders have blogged about the lengths they went to retain access through a tube to the bow section in which the bow-eye must be installed, so failure to completely isolate this area from the liquid foam products and their chemical reaction can make subsequent bow-eye installation a challenge. (That said, at least one builder installed the bow eye before putting in foam.)
I actually bought the requisite two cans of product when I was at this stage but ultimately never used them, deciding to use foam blocks as in the manual. I'd love to send these to you if you decide to go this route, so PM me if you want to.
Stay safe and wash hands.
All the best,
Mark
"Puffin" 2018