Quick question:
If using shoulder screws do you still need to use bearing blocks? I wouldn’t think so but I’m not too sure. Thanks! 
Nope.
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No, in fact you can’t. There’s no way you can get the short shoulder screws through two bearings.
What we found works best is if you have the two pieces of aluminum, and between them a plastic washer. The plastic washers usually won’t slide right on, so some force is needed. Then, use a normal nut and tighten it all the way. But be careful, if you look at a nut the two sides are a bit different. With one side you will tighten and squish it onto the metal, but with the other it should hit the non-threaded part of the shoulder screw right before the metal, giving you a well turning but still solid joint.
You can use shoulder screws with bearing blocks with a little persuasion from a hammer. Makes for a pretty tight fit. You will have to use kepes nuts as the nylocks will not fit on the remaining thread.
Ok thanks everyone. I haven’t actually used shoulder screws before so I wasn’t aware of how short they are.
In some ways they are too short. Three layers of steel is ideal for the length of the shoulder, not two. So an extra sandwich layer may be needed at times. One layer of steel and Delrin “jam it through with a hammer” technique is what to expect there. Use a vice for those.
But shoulder screws don’t give the opportunity to slide around in the square hole like a normal bolt does which is very nice for high strength connections.
Keep in mind that you can always order shoulder screws from other websites such as McMaster-Carr. They don’t have to be the same size as the VEX shoulder screws (or have the same head or anything), you can buy any length up to 2", as long as they are the same thread type and screw size.