Hi Peter, I agree those cars sure look nice. The answer to your question about overhang on your inner loop depends on your distance from center rail to center rail. The only way to know for sure is take a 21" car on the outer loop and your largest car on the inner loop and hand run them around the curves checking for clearance. You may be OK, you may need to move one of your loops a bit to provide extra room.
If you don't have a 21" car you can always make a mock up by adding length to your longest car that you currently own, or borrowing a 21" car for testing.
I can't pull the trigger on these beautiful cars and somehow know I will kick myself down the road, but I made the decision to stick with 18" cars. Hope this helps.
Paul
