jit.gl.gridshape trail/blur processing using poly~

Dear jitter ninjas - (jitter n00b alert) - I'm after some help getting some interesting trail/blur effects on some openGL shapes I'm manipulating in a poly~. I've found an example or two of the effect I'm after in the forums (e.g. https://cycling74.com/…/jit-gl-mesh-then-gaussian-blur-ove…/) but can't get these to work well in my case.

Question - if I am processing multiple jit.gl.gridshapes to their own individually named textures inside this poly~, can these be sent to a single jit.gl.slab/jit.gl.videoplane outside of the poly~ for processing? Or must they be rendered separately?

I'm trying to do some slab processing on multiple gridshapes and having a hard time getting the output I'm after (very low res - not all my gridshapes appearing - funny quirks jumping between floating/fullscreen window). Initially I was rendering each gridshape to the main window, but I learned to process these I need to use the 'capture' attribute and process them as textures using slab.

Attached below is an example of what I'm trying to achieve - both parent and second code for the poly~ abstraction.

Any help would be appreciated, thanks!
(NB Question also posted on the Max/MSP facebook group - if I get a solution there I'll update here - thanks for understanding)

Parent Patcher:

Poly~ abstraction 'poly_boids_forum':