Re: Problem using fasteners through multiple solids.
the Simulate's internal Fastener tool works only between two components.
If you want a screw/bolt that intersects three or more parts you have to use a "solid screw" with preload. If you use Creo 3 there is a specific tool named "preload". For the previous releases you can utilize a thermal load on a solid element or a beam.
What you've done with the springs is another workaround.
Remember that if you are interested to have a detailed view of what happen near the screw/bolt hole, you need to use contact regions between between each parts, with or without friction depends always on the level of detail.