scope mount location and POI

I recently purchased an Armada, and now Ive got miles and miles of rails. I made a simple phone mount for my scope using plumbing couplers and pvc. It puts the phone too close to my face.

I am new to picatinny, so the question is, if i move the scope forward to accomodate the phone mount, and backwards when Im not using the phone mount, will that affect accuracy? if i move my scope do i have to re-zero it every time? or is picatinny pretty consistent?