Gavin,
I'm not sure I am qualified to answer as I have only ever had 2 weaners, last year. I found that whatever I put their feed in they would upend it in no time, regardless of how may rocks weighed it down.
Instead I put a couple of paving slabs in their pen and fed them on that. As MAK has said if its on solid ground then there isn't much waste. Having said that I found that as they got older, and stronger, they upended the slabs too and broke them. Will have to get bigger, heavier slabs next time.
I put the slabs nearish to the fence, but not too close (didn't want them rooting under the fence) so that on very wet, muddy days I was able to throw the feed onto the slabs without getting into the pen myself.
With regards to water, no matter what I put that in they always turned it upside down and I was worried there wasn't water there when they wanted to drink. So we bought an auto waterer that was attached to the fence. As they drank it filled up. We had the reserve water in a big black plastic tank, outside the pen, which we filled up every couple of days or so.
I hope this helps.
Have fun with them
Sally