Thanks for the tips and encouragement TBH I wouldn't have tried my router on aluminium... so something new to try.

Some general questions from reading and looking at some of the designs.... What strikes me is there is a lot over engineering in frames etc. Ok that's needed in context of cutting duty.
I'm thinking MDF, Plywood and Aluminium plate, with 3- 10mm cutters I assume.

Some of the frames are huge steel welded section, the likes which I've made/designed in the distant past to hold large diesel generating sets.... Then heavy steel gantries on top.... Seems OTT for such cutting duties.

I'm not expecting to machine steel billets, for a start I'm thinking of a Kress 1050 spindle, which I guess could be the limiting factor on loads.
I also want to use 3 4mn Nema 23's... So I have an eye on the weight.
Having looked at the designs here I'm reluctant to post my CAD design now, as its a way off what I see. For example running FEA analysis on say a single 1200mm length of 25mm x 200mm Marine plywood gives 0.0X range of deflection with a 50 Kg load.

So little puzzled at present....... I've kept it to aluminium, thinner sections and orientated in the direction I expect the load and bolted.... ie trying to consider the "I" value/Second moment of area.
I have an open C sections to refine at present, a brace across could do it.

That said some impressive machines on here.....
Happy New Year...