Hal,
Thanks for clarifing some of that for us. I too have done a lot of work in the free rolling truck area. After extensive testing I have found the best freight truck combination is Kadee metal sprung trucks refitted with Intermountain wheel sets - with a very small drop of oil in each journal during assembly. Re-oiling has never been necessary.
I tested this combo against every type of rigid sideframe truck and wheel set combo I could come up with. The Kadee/Intermountain combo was consistantly the best. The other two advantages are the sprung/equalized desgin tracks better and the extra weight it automaticly adds at a low center of gravity. I have actually stopped weighting cars to NMRA RP's and now use on 70-80% of those numbers with better results.
I have some of the same locos you listed and your drawbar results are similar to mine. Many of those locos I do not own as they do fit my modeling scheme/goals and I do not "collect". I have curves a big as yours but still avoid locos like the 2-10-2 and 2-10-4. I have all three of the articulated locos you listed as well as Proto 2-8-8-2's, they all are good, but the 2-6-6-6 and the 2-6-6-4 (mine has the traction tires) are by far the best pullers.
I have Proto 0-8-0's with and without traction tires, yes, there is a BIG difference.
One loco I have that's not on your list is the PCM Reading 4-8-4, it is a very good puller as well but did need some "tuning" out of the box. It was tail heavy do to a large space in the smoke box left for a future smoke unit and needed weight to balance it, and the tender frame needed grinding to clear the drawbar for close coupling.
It appears you do not have the best Spectrum loco of them all, the USRA Heavy Mountain. I have six of these and all run very smooth and pull very well. My tests put their drawbar pull at 3 oz or better. the Spectrum K4 is known for being wimpy, but reports are the newer ones are better. Again, don't have one myself, don't model PRR.
I add a little weight to my Spectrum 2-8-0's (I have eight of them) and am very happy with them. Double and sometimes triple headed they handle 25-40 cars trains with no problem on my 1.8% grades.
As for grades, I like to keep them much easier than 2.5% and typical train lengths here are 30-40 cars.
Bachmann customer service is very good, sometimes slow, but always a good result. So I'm sure they will get you taken care of.
Sheldon
One other note - in rereading your orginal post you mentioned poor slow speed performance from the Spectrum 2-8-0 in both DC and DCC. I use DC, Aristo Wireless Throttles which have pulse width modulated DC - EVERYTHING runs as good or better than it does on any other DC or DCC throttle I have ever seen. My 2-8-0's that where a little lurchy before, are great on this throttle.
As for DCC, everyone I know has gotten better performance from Spectrum locos by removing the factory circuit boards and hard wiring good quality decoders in them. Simply plugging in decoders does not seem to work as well.