I have a 57#@28 MAII.  I am trying to tune CX-250s.  I have a CX250 that I cut 28 3/4" (drawing 28").  I want to use 125gr broadheads.  I have added 210gr to the back of the insert (using Gold Tips weights), and it still shows a little strong.  I bought a test field point kit from 3Rs.  With the 145gr field point, it shows true.  

The question I have is if I keep adding weight to the rear of the insert, does the weight increase not change the spine as much, once you have that much weight?  I ask this because my weights are already about 2" long behind the insert, and the field point of 145gr is in front of the insert. Should I keep adding weights or look at tryiny a 145gr or 175gr broadhead?

So you didn't bareshaft tune these? How much weight do you have behind the insert? You might be better served (if you are just using the standard aluminum insert) to put some 50-100gr. brass inserts in the shafts with the 125gr broadheads. I shoot a similar bow/arrow setup. The CE Heritage 250s I have found cut to 29.5" w/ 100gr. inserts and 125gr. tips to fly perfect. So you have cut them down too far I think. You will have to put more weight up front to make them weaker. Just screwing in weights is not as effective as getting that weight at the tip.

up your tip weight, sounds cheaper and easier