I now use 15mm x 25mm wall, pipe insulation, if I lived near the sea I would get those 5ft foam swimming floats which are solid foam ??? which are sold to send children out to sea. :
A 43" or 48" AeroMarine Challenger with "Pool Noodles" (think that is what those swimming floats are called) fitted in it chines will float equally as well upside down as right way up - even to the extent that my boat's engine was
still running when upside down.
Foam only in the bow invariably means that if your boat sinks it will go "swan up" and your radio gear is under water.