The larger orifice and 10-inch spray fan of the 517 tip you used is way too big for polycrylic and cabinets. Bubbles formed in the finish because the polycrylic was over-applied. The recommended spray tip sizing and pressure on the product label is often inflated. The reality of those specs is you almost always have to use a smaller size than what's recommended on the label to get the right results. A good size to use is a 308, or a 310, using the green FFLP tips explained in my article. You need to use the blue RAC-X tip guard with the green FFLP tips. I have no idea if the nozzle threading on your particular spray gun is compatible with the blue RAC-X guard, but you can call Graco customer service and ask. For spraying pressure, start low and test your spray pattern on a piece of cardboard. You want just enough pressure so there's no tailing (fingering) on the outer edges of your spray fan but atomized enough to lay down on the surface. Too much pressure will waste more material and over-apply if you don't move the spray gun fast enough.