Dennis,

In my limited experience, it is hard to implement a UML design in any language - OO or otherwise!

However, some UML is better than having no modelling or formal design at all.

If you haven't seen it already, have a look at

http://www4.tpgi.com.au/users/void/bkauler/

where Barry Kauler discusses an interesting design methodology which is aimed at real time systems. His book, 'Flow design for embedded systems', is also an interesting read.

Rgds,
Derek