downsize,and would this small amount affect the design,especially if it is a lace type?

If your machine does 5 x 7 a 5.7 design needs a 12% reduction - far too much to contemplate when FSL is concerned, I would never try more than 1% in that case.

If your machine only does up to a 5 x 7 do not buy anything larger, some things can be sized down with the right software but especially lace will not work well.

This is strictly a hoop area issue. If the design is 5.7 x 6.9 that makes the design 144.78mm x 175.26mm and if you have a hoop(example Pfaff 140x225)it will not fit inside the stitchable area. In most embroidery designs you could reduce the size that small amount to make it fit without much trouble, however, not so with free standing lace which most digitizer will tell you - do not resize!

Lace designs should nor be resized. You will probably end up with a mess on your hands because it may fall apart.