When I bought my 410 2 years ago one of the stanchions was pushed in, and the 2 machine screws outboard had no heads. I thought it was going to be a big deal but I removed the remaining inner machine screws and unthreaded the stubs of the broken screws in a couple of minutes. I got the replacement extra wide truss head screws from McMaster Carr.
Chandleries will not likely have these screws but I would not be tempted to replace the truss head screws with more common pan head screws which have a thicker head. Having the head break under excessive load is preferable to having the threaded portion break or the threads in the embedded aluminum plate pull out.
94792A736 316 Stainless Steel Extra-Wide Truss Head Phillips Screws, 1/4"-20 Thread, 1-1/2" Long, Packs of 25
Good luck -- Ian