Hey JazzCNC thanks very much indeed for that it sounds like I'm on the right track now, I did think about top and bottom but thought this might split the forces between up and down and back and forwards although doing it this way I guess the loads are on a single rail more for each movement. So will do I will go top and bottom which will be great to get rid of some of the material around the back. I didn't really want it there but it was the only way I could think off to get the rail around the rear to also try and keep it out of harms way too.

I am really sorry when you say move the rails back do you mean so that the spindle is inline with the upright box section of the gantry ? would it maybe worth going for something like 100x50mm box section for the sides and then put the 50x50 towards the rear to the spindle so it is more inline with the uprights of the gantry, I'm sorry if I've misunderstood.
Also on a side note I would like to thanks you very much for helping so many people on this community I have learned so much from you going through many peoples posts and its great to see people just trying to help each other out.

Also EddyCurrent the same goes for you going through peoples posts you are very helpful I just hope that I can get a machine running to be able to get the knowledge to put something back in.
Don't worry I'm not always a soppy sod.
I thought I might have the blocks a little too close but just picked the figure out of the air really for the distance. Is there an optimum or a way of determining the best gap ?. like most I was trying to maximize the cutting depth but because the bed moves I will add some more distance on it and just move the bed on each time I have a thought to making some fiberglass molds with foam for a dash board and though the more depth the better but I guess it will give a worse cut for other things I will have another go at it and go more in depth on the design now I know where I'm going with it all.

thanks chaps.

Rob