I have some ff 12 strand strings and wanted to try them on my silvertip with antler tips(non-ff) like the other posting is a 12 strand padded to 14 enough or should I get more padding in the loops?

A lot depends on the type of FF string and the poundage of the bow.  I'm happy with 14 strands of BCY 10 on my 40# bow.  I would say that the loops ought to be at least as fat as loops made with dacron.  For some of the more modern FF strings, that would be more than 14 strands.  Since you're going to use it on a non-FF rated bow, you probably should go a little fatter than dacron, and add more strands for heavier weight.

The limbs are 66@30 I draw 27 = 57 at my draw 536 total arrow weight. I have 12 strand  D10 strings padded to 14. the b55 14 strand I have are very hard to get quiet.

For 57#, I would pad it until it is as thick as 16 strands of Dacron.  Not knowing anything about D10, I can't tell you how many padding strands that would be.  Perhaps one of our stringbuilders will see this and chime in with more precise information.

I took a quick look on the internet.  Is D10 the same as BCY 10?  If so, it's the same stuff I use, and to me it seems about the same thickness as Dacron, so I use an equivalent number of strands to get the same padding effect.

I don't know if these pics help at all..  If it handled a dry fire from 68#, I think it should be good.

If by D10 you mean Dynaflight 10 (now labeled as "Force 10), it's basically the same thing as Dynaflight '97.  12 strands in the string is a good choice IMO, but I like 18 in the loops.  

As long as it fits the string grooves, I don't think you can use "too much" padding, especially on a non-ff bow.

14 may be plenty, but I rather err the other way.

Added a couple pics above.

Frankly, if it were me, I wouldn't risk it with 14 strands in the loops.  Since you would have to remake the string loops to get at least 16 strands in the loops, it's easier to just get a new string. Better to save the old string for something else.  Strings just aren't that expensive to be worth risking a bow on.

How many strands do you think this is padded to, and how much more do you think it could go and still fit?

Depends on the material.  You can un-twist in the middle of the string and count the strands and that might give a clue.