CR-10 Fan Duct Mod w/Thicker Bolt Standoffs

This is a remixed version of the fan duct mod published here by Nexi-Tech.

I increased the thickness of the bolt stand-offs as I was finding the originals to be a bit too thin and would easily break due to accidental over tightening of the mounting bolts (the stock fan duct suffers the same issue). This is a far more robust design and the stock bolts are plenty long enough to accommodate.