good question about whether you can run the tray and splash guards with Chris's bumper!
Getting hold of replacement fixings is jot a problem (common across all sorts of Honda's of that era, incl NSeX

) and I find if you re-assemble them with copper-ease, they're ok next time you come to them.
My analness won't let me run cars without them, but regardless of that, the splashing around of crap up inside the arches/behind thew front lights, chassis legs and over the front of the doors and A pillar is a big no-no for me!