Big Boy pulling question

Hello everyone, this is my first post on Railworks of America. I have been following these boards for about 6 months now and I have to say the quality of ppl is just amazng. No trash talking or insulting, vary rare in todays standards.
OK I just bought the Big Boy addon from ICC and what an amazing looking model. My question is about the engines pulling power, I need to know if Im doing it all wrong or if this is normal behavior. I started out on a freeroam senario, Challenger at Barstow-Barstow to San Bernadino. The area of the map starts you off on a 1.9% grade. I used 19 flatbeds with Sherman tanks on them and hooked the Big Boy to the front. Now before Railworks 2 came along there were options to play simple, intermediate or expert. With Railworks 2 it seems that u can only toggle the simple operations box in the options, so i dont know if there is a true difference between intermediat and extert now.
Anyways, I dont have the simple option checked so i have access to the steam engines throddle and reverser. I started by putting the throttle and reverser to max, dont know why reverser only goes to 75%, and the best I could do with the Big Boy was about 4.3 mph. I checked a few other steam engines out, Southern Pacific, and the Challenger, both were worse off than the Big Boy. Hell the Southern Pacific even started to be pulled by the train cars.
I then hooked up the 19 cars to a ES44-AC diesal and that locomotive was able to get the train up to 12mph rather quickly. I know i read something about dieasles being able to use all of there horsepower from the beginning while the steam engines need to build up. I dont know if this is the case or if Im doing something in correctly or if the pulling physics or off for steam engines. I just thought the Big Boy would be able to muscle through that load..then again 19 tanks could be pretty heavy. Any advice would be appreciated.
OK I just bought the Big Boy addon from ICC and what an amazing looking model. My question is about the engines pulling power, I need to know if Im doing it all wrong or if this is normal behavior. I started out on a freeroam senario, Challenger at Barstow-Barstow to San Bernadino. The area of the map starts you off on a 1.9% grade. I used 19 flatbeds with Sherman tanks on them and hooked the Big Boy to the front. Now before Railworks 2 came along there were options to play simple, intermediate or expert. With Railworks 2 it seems that u can only toggle the simple operations box in the options, so i dont know if there is a true difference between intermediat and extert now.
Anyways, I dont have the simple option checked so i have access to the steam engines throddle and reverser. I started by putting the throttle and reverser to max, dont know why reverser only goes to 75%, and the best I could do with the Big Boy was about 4.3 mph. I checked a few other steam engines out, Southern Pacific, and the Challenger, both were worse off than the Big Boy. Hell the Southern Pacific even started to be pulled by the train cars.
I then hooked up the 19 cars to a ES44-AC diesal and that locomotive was able to get the train up to 12mph rather quickly. I know i read something about dieasles being able to use all of there horsepower from the beginning while the steam engines need to build up. I dont know if this is the case or if Im doing something in correctly or if the pulling physics or off for steam engines. I just thought the Big Boy would be able to muscle through that load..then again 19 tanks could be pretty heavy. Any advice would be appreciated.