Hello,
I just finished installing an Aguilar OPB-1 in my MM-Stingray clone (OLP) and here are some pictures.
The preamp is glued to the plate and it fits exactly in the control cavity.
I routed a hole in the back for two batteries (18 Volt) and drilled a hole to the control cavity.
The pickup is connected in parallell to the volume pot.
It sounds great! Powerful bass and nice treble!
It's well worth the extra money and a couple of hours work.

Greetings.
W2L