Thanks all,

I would run ropes under it but it will be on and off all summer and
permanentley moored so that would be a bit of hassle.

I also like the idea of stretching it below the rubrail, I have seen
this done on open fishing boats and works well, but our boat has a
cuddy so it is not uniform all the way round, we have threaded the
bungee in and out the tarp eyelets all the way round...so Robert
whatever you have on your boat is what I am looking for.

Think i will go with small cleats (like the ones used for tying boat
up) under the rubrail and up and over the cabin, then strech the bungee
over them.

Thanks for the input all.

Dave