This morning dad and I went down to the local park to continue with the staging mechanism test flights. This was the third separate set of test flights, with minor failures on the first two sets. We finally got the stager working properly today on 5 out of 5 launches so we were happy. We only flew the stager on a small booster (2.1L spliced pair) and a 1.25L second stage. The flights were done at 110psi and 120psi.
Next we'll need to test it on a larger rocket a few times, but will need to take it to Doonside for testing as the local park would be too small for it.
If the next set of tests proves successful, then we'll post a full tutorial on how to make it.