Hi Latch
As Shermie says, I'm working on the problem. I'm involved with the Panther build at the moment, but will get back to the Achilles when the Sherman build starts.
Anyway, The Acadamy Kit comes with 5 spare 17 pounder rounds to help you out. I have made a mould of these and will be casting them for the Achilles I have. They do not need to be high quality 'cause you aren't going to see much of the rounds closer to the hull when it is all together.
I have made the cast by temorary glueing the edge of a piece of 40 thou plastic card (with white glue) to the kit rounds. It is glued almost along the full length of the round - basically, head on, it looks like O---. The casting rubber is poured so that the plastic card sticks straight upward out of the rubber. This will leave a long open lip so that you can easily fill the mould and retrieve the rounds by spreading this opening in the mould. Just make sure the mould is thick enough to prevent the opening from expanding by itself. The resulting casting plug line will need to be removed and cleaned up, but if you make a mess then make sure the line is at the back of the round when you fix it to the rack.
In regard to the internal racks, the kit ones are for the superflous M10 round canisters that they incorrectly supply. You will need to replace them so the 17 pounder rounds can be fitted - no big deal, just use the kit parts as a template to cut replacement plastic card.
There are a few other minor things with this kit. If you buy it and want help, or want a pic of how the corrected interior should look, drop me an e-mail.