1911 Double Fire ?

I would say that after 1000 rds the springs were a little on the weak side. Look at the sear for signs of excess wear and replace all the trigger assembly springs.

The gun is terribly dirty, the sear is bouncing off of the hammer, or the geometry is wrong. Is it clean? What is the set weight of the trigger right now? Do you have a GOOD trigger pull gauge? If so what is the set weight on the sear leg and the disconnector leg of the sear spring? What were those weights when you set it up? Did the pull weight change since you installed it?

Sear springs in a 1911 will last virtually forever, at least several hundred thousand cycles. I really don't think the spring is the problem even though the TI spring from SV is not a part I have ever used in one of my guns.

Last, STOP SHOOTING IT!!!! It might go full auto until empty on the next pull.

"...What may be causing the gun to double fire?..." Light cast bullet loads will do it. So will a light trigger and failing to follow through. You may be 'bumping' the trigger under recoil. Have a look at the firing pin and spring too. If either is busted the firing pin can stick out and cause doubles.