Just a fyi for anyone building a Herculien, trimcraftaviationrc has added some new items since the BOM was last updated. I think the following are are equivalent to the mcmaster parts, but cheaper, at least if you’re looking at stainless steel versions. When I ordered parts for my Eustathios, I pointed out the printer BOMs and he was nice enough to add a few more items to his inventory.
3mm oversized flat washer (Din 9021) - http://www.trimcraftaviationrc.com/index.php?_a=product&product_id=458
5mm oversized flat washer (DIN 9021) - http://www.trimcraftaviationrc.com/index.php?_a=product&product_id=459
5mm x 10mm button head screw - http://www.trimcraftaviationrc.com/index.php?_a=product&product_id=456
5mm x 12mm SST socket head cap screw - http://www.trimcraftaviationrc.com/index.php?_a=product&product_id=451
5mm wing nut (DIN 315) - http://www.trimcraftaviationrc.com/index.php?_a=product&product_id=455