Of course ever soil is different and field cultivators aren't all created the same but .... as a rule of thumb how many horses per foot of field cultivator do you use?

I've been all over the board in the past in regard to my question. In the 2000's we pulled a 36 or 38 foot Tigermate II with a 7250 Magnum which would have been around 7 hp per foot. We later pulled the same field cultivator with a New Holland TJ 325 which would have been 9 hp per foot. 

I'm looking for a different field cultivator currently to pull behind a 400 Steiger. Using past experience  suggest I can pull a 56 foot cultivator with 400 horses and be comparative to the 7250 with a 36 footer. Or, I could pulll a 44 footer with the 400 and be close to the preformance of the TJ 325 pulling the 36 footer. Both tractors in the past were more than adequate. 
gr
I believe anything between 44 and 50 will be where I want to be. 

In addition to the hp/ft question I wonder how weight and tracks versus tires changes the equation. The Steiger weighs more than 51000 pounds and is on tracks. Would it be safe to say hp/ft decreases, slightly, as weight goes up and again when tracks replace wheels. 

Another way to look at it is a 20000 pound weight advantage giving an adantage over a similar hp/ft lighter tractor? And, will tracks also provide an advantage over wheels in a similar situation. 
Long/short. If I'm satafied with my hp/ft won't tracks and additional weight give an even greater benefit?