I found it difficult to adjust the trackpad’s position so that it had just the same amount of space on every side to move freely when being clicked.
What worked for me was putting all four screws in - but a little loose as suggested - and then putting the button case back on (without screws) for protection. Turn the laptop in normal position, open it, adjust the trackpad, fix its position with one large strap of of easy to remove tape - approximately 15 x 4-5 cm e.g. masking tape.
This will hold the trackpad in position while turning the MacBook Pro around and tightening the screws.