OP -

if that is the 4130 cromo version of the boardwalk it would be worth it to upgrade and modify it. in my opinion, that sleek and skinny frame is one of dahons better looking machines. however, i wouldnt advise trying to make it something that its not, i.e. a road bike. if you are going to spend 500 bills you would be better off locating a used bike friday. that being said, there is a lot you could do with a boardwalk frame. even dahon agrees:



to determine what type of handlebar stem will be compatible with the version you have, you will need to fold the stem and note which type of assembly you have. if you have a hex-drive lock-nut that threads to the inside of the fork, then you can order a dahon "radius" stem. if your have the older type, you will need to locate a folding stem with the quill type insert.
quill type:



radius v type with hex-drive exterior threaded locknut: