My honest opinion is that you are wasting your time with this gantry setup if you want to use it for a router as it's just not strong enough and certainly would be wasting your money trying to fit a 1.5 or 2.2kw spindle to it. The Single narrow beam just doesn't offer enough support for the Z-axis, really you need another above the lead screw so it offers support for the Z-axis backplate.