Hello Mike,
Your frames look absolutly great.
My TurboCad Pro 8.1 is also a fine instrument to try out the construction of the part I would like to model. As you said, one can find out if things will fit, even before buying the neccesary materials.
Unfortunaly I'm not familiar with your Alibre, but in TurboCad Pro the program slows down too, if you use too much complicated parts, like bolts with thread.
They advice to use so called "Blocks", which are all vector copies of one stored original within the drawing. It helps to reduce memory space, especially when you use a lot of the same parts.
My way of working in 3D-CAD is, to set up a drawing (1) with the most important measurments. From there I copy a part to a new drawingfile to work it out. (Don't change the reference points)
After finishing the "sub" drawing I check the reference points again in my number 1 drawing by putting back a stripped copy of the "sub".
For instance for an underframe I draw the buffers, wheels, brakes and so seperately in the way discribed above.
Let me show you one of my axlebearings.
Lots of succes and keep us posted.
Frits
Build it perfekt, but keep it simpel.