If you use factory recommendation when reusing stretch bolts, they will be over tensioned and likely to break.
Example: I reused my bolt to hold the timing belt pulley to the crankshaft.
I checked with a few bolt manufacturers and with the info obtained and an educated guess as to the bolt strength, I decided 300 Ft/Lb. would do.
The recommended tensioning is 148 Ft/Lb. plus a further 180 Deg. (A half turn)
I tensioned it to 148 Ft/Lb. and then by turning it a further 20-25 Deg. it reached 300 Ft/Lb. I am pretty sure it would have broken before it got near 180 Deg.
So, as stated earlier: Just tension as you would a standard bolt of that size.