Mike, you should be able to do 27" radius with little problems for most equipment. All of AM's freight cars have body mounted couplers as do MTH's (SHS's) and S Scale America's (DesPlaines Hobbies.) Full length passenger cars would be a different story with body mounts. Here's an AM 85' Pullman with body mounted Kadee's sitting on my 27" radius test curve:
With body mounts, these cars will traverse my 33" mainline curves OK, but are less reliable on my 29" radius passing sidings. I've stuck with the talgo dummy couplers on my AM 75' Budd cars because at this point I see no real advantage to body mounting Kadee's. Plus, I'd have 24 cars to convert...
As far as Lionel locomotives go, the EMD SD70's and GE ES44's will run on AC, DC, and DCC. The U33C's will not run on DCC, nor will any of the steam locomotives, but they can't be easily converted to scale anyway.
Bear in mind that they can be finicky on conventional DC. It depends on the power pack. Mine run fine on DC from my ancient MRC Controlmaster X or GML Enterprises DC throttle running off an MRC pack, but can gets erratic with some of the newer power packs.
Lionel worked hard to get the bugs out of DC runnning and post 2013 made locomotives should reflect this.
DCC operation is fine. I know Lionel debugged the DCC for at least 4 different DCC manufacturers. I use the MRC Prodigy with no problems.
One thing about the SD70's and ES44's-- The pilots swing:
This is to help these loco's deal with Flyer curves. The SD70's include hardware to anchor the pilots, the ES44's do not. Both do include Kadee mounting hardware. I did a post on how to anchor the ES44 pilots HERE.
With the pilots anchored, I'm not sure how well these loco's would do on 27" radius. Here's an SD70 on my 29" radius:
Still runs without derailing, but is pushing the limits of the Kadee coupler swing on 29" radius. I think there might be problems on 27" radius.
I hope this information is of some help.
Rusty
