I didn't ask them to put in the Minis as I didn't realise that the Super Mini was quite so ineffective. I'll do the vent myself but I think large rectangular holes are a bit beyond my competence!
I agree it is a somewhat more serious operation. However, it needs to be done and if the yard doesn't do it, there will be a boatbuilder near you who will do it for you, and in a jiffy.
There is a stencil for the cutout in the Andersen Mini box, you draw the outline onto the hull, drill a proper radius hole in all four corners and connect the holes using an electric jigsaw. You smoothe the cutout using a small drill with a router bit until the bailer fits well in. You then drill the fastening bolts through holes, and sink the holes underneath the hull.
Very important to seal all drill holes and coutout edges with one or two coats of Epoxy, and when you set the bailer in, use Sikaflex generously. Finally wipe off the surplus Sikaflex, ready.
The boatbuilder doesn't do it differently, only he does it quicker, and doesn't make mistakes.
It is not complicated or dangerous, but a mistake can be made, so I would really hope Swallowboats starts doing this for all its customers. It's an important improvement for the waterballast system of the plastic BRs. (The wooden BRs are different there.)