When I first built my Shapeoko2 the only spindle I had on hand was a 1.5kw water cooled 80mm dia. spindle. And since I was building it with a 1 meter wide gantry you can imagine there was measurable amount of twist on the gantry. I cured this by inserting a “T” shape extrusion I found that had a thickness that perfectly filled the void between the two maker slide extrusions that make up the gantry. When the assembly was drilled and bolted together, it gave me a gantry that was very strong and handled the weight of the big spindle with very little flex or sag.
I ran the Shapeoko like this for a few weeks until acquiring a Quiet Spindle. There was a slight difference in noise level with the new spindle, but the biggest change was a noticeable increase in “snappiness”. With the reduction in weight the X axis could really zip back and forth and the occasional lost step in the X axis disappeared completely.
The really nice discovery was that there was no loss in cutting ability. The much smaller 300w spindle handled all the cutters I was using with the larger 1.5kw spindle perfectly. I’ll note that I have only tried cutters up to 1/4" diameter and smaller. Bigger router cutters may perform differently, so, YMMV.
Larry