Based on info from manufacturers, I've always installed mine at 55% compression, 45% extension.
For instance, if your shock has a travel of 5" like the ones you have there, 55% of 5" would be 2.750", so....
The ideal length of shock for your application would be 12.500" extended and 7.500" compressed with your mounting dimension of 10.250". That would give you 55/45.
(10.250 plus 2.250 equals 12.500 or 45% extension from rest)
(10.250 minus 2.750 equals 7.500 or 55% compression from rest)
