Merry Christmas to you Joe!!!!
Having had 2 layouts on doors, I found that 11"r was a good radius for 4-axle locos and 40-50' cars.
I did run 6-axle power but tried to stay with small 4-axle engines The little Kato NW-2 is an excellent engine for this size layout. I also used Atlas GP-38's and 40's as road power.
Stay with quality track like Atlas or the Kato UNITRAK and you will be very happy!
Good luck,
pc