Building Harrier Uundercarriages...

[Radish]

How to make sure everything touches the ground?

Add the nosewheel and outriggers.
Adjust appropriatly to ensure all is lined up, the fin verticle, etc..
Then I "fix" the outriggers eventually with a dribble of superglue to make them totally unmoveable.
Lastly fit the centre main u/c and adjust as appropriate to ensure it touches the ground.

 

[Hobbes]

Good point. My instinct is to fit the main and nose gear first, and then try to add the outriggers. Your way has a better chance of succeeding.