Hey Nyssa, Couldn't you dig a hole for either a ex shipping crate - or the dome idea
http://www.domaindomes.com.au/ and if you really want to be overkill (as you say probably quite rightly so that the crate couldn't stand the weight ... Couldn't you simply pour some concrete over it ? Once it's set you'd be right yes ?
It's extreme but maybe that would be the safest way to go ... But what do I know I'm a musician. I sometimes WISH I had experience in house building for this exact reason.
