I was attempting to build this FPV racer and realized I did not have the appropriate standoffs. I have ordered some brass ones, but given the amount of fasteners and overall rugged design of this aircraft, I found that these standoffs, which I made just for the sake of testing the assembly until my brass spacers arrived, actually held the quad together very strongly.
Be careful of elephant foot when you print, as too much squish will deform the bottom and ruin the threading.
I print them at 100% infill, and 0.15 layer height for strength and dimensional accuracy. They are threaded with M3 threads, and my M3 bolts went into them nicely. Don't overtighten, as they're easy to strip.
I would always suggest a metal part over this option, but if you're stuck as I was, it's a quick print option.