Although the website is still active, i don't think the decks are still available, as people in the past got no response when trying to contact the owners. So unless things have altered recently, caveat.
In regard to fitting bayonets- nothing difficult on an unbuilt kit, but to fit one on a finished sub would require the removal of the techrack, which is no small task as it's bonded into the endcap.
The standard system does the job, the thing to remember is that Robbe used a special extra soft o-ring for sealing. So if you need to replace it, you really either need an original part or source special extra soft compound o-rings, otherwise you might get leaks.