I think I could seal the openings with judicious use of some sealant (butyl caulking, et al), but I'll give it a go first to see if anything seems unusual.
The plates and connectors pictured. Front Panel Express did a nice job; better than my photography skills. LOL. Any anomalous marks are smudges or dust on my behalf.
Got the crossovers removed and the bi-amp plates/jacks mounted on the speakers. Whipped up some cables this AM from 14/4 SJOW portable cordage left over from an old non-related project. Red/black = LF +/- and white/green = HF +/-. Might even get it fired up today.
Next Digi-Key order may include color-coded banana plugs to make amp connections easier.