Top tips for Stage 1:
The 'pass mark' for each test is more of a trade off between speed and accuracy. For example, the 'cubes' test has 40 questions in 20 minutes.
On this basis, if you completed 40/40 questions and got half wrong, you'd fail the test (Poor accuracy)
If you completed 35/40 and got 5 questions wrong you'd pass. (Good trade off)
If you completed 20/40 questions and got them all correct, you'd fail. (Poor speed)
Similarly, with regards to the 'diagramming' test, it works on the same logic, but a bit more room for error I believe.
On this basis if you completed the whole test 50/50 questions and got up to 35-40 questions correct, you'd pass. (Good trade off)
If you completed 20/50 questions and got them all correct, you'd fail. (Very poor speed)
Hope this helps.