An interesting challenge. Knowing how wide your hand is would be a big advantage. Also using a proper PU blank with known dimensions would help. A solid block of EPS foam would make things much harder. I say go for it.
Couple of years back I was having problems with a neighbor and did not want to risk them calling city hall on me for making boards. I did a couple of boards without the use of power tools. A really sharp low angle block plane works just as good as a power planer......you just have to make a lot more passes. The same principals apply.