Thanks it looks like that's exactly what I need.
I found also what I was doing wrong in making the higher resolution shadow map texture - I wasnt changing the viewport size to match the texture when I enabled the frame buffer.. It works great now - I'm working on switching textures based on the camera's distance from the shadows now - it's a bit tricky though considering the shadows can all be at different depths in the viewing frustum.. I'll figure it out though
Thanks for the help