To answer your original question, the center shot on mine is 15/16" but I'm still using the TRG so that will have some effect on center shot.
Not too sure about the other issues you are having though, with the string/cables at the correct lengths......DW should be +/_ about 1-2#s of the spec listed on your bow, did you check peak DW prior to disassembly ?
I don't think your speed lose is due to the new string set, 24 strands of 452X is the same diameter as 22 strands of Trophy and a 24 strand 452X string will actually weigh slightly less than the same string made of 22 strands Trophy, if all serving specs are kept the same. I didn't lose any speed when i built the 452X set for my Onza.
You may want to look at the cams and how well they fit in the limb forks and how freely they rotate, could be if the dip was slightly thicker than the factory finish, the cam bearings have a bit more pressure against them not allowing them to rotate as freely as they did before. Speed nock locations should be, 3 at each end starting at 14 7/8" from the end of each loop.
I checked my cams and they rotate freely. the dipping might have caused a tighter fit in the limb pockets and stuff, still doesn't make sense on the speed loss. like I said I was getting in the low 270's before.It seems the only real difference is the strings.If it didn't shoot so good I'd put the old strings back on and check it.I'd rather have it more accurate, than fast, if I can't have both.