More pics.. There were a few spots where sections of ply were missing completely, having split away from the cab, which i had to repair. In the 1st two pics, im using Builders Bog to replace the missing ply. I clamped a piece of wood to the inside edge with a piece of paper wrapped around it to stop the bog from sticking to the wood i had clamped there as a guide. Then i simply filled the space where the ply was missing with builders bog! simple and effective me thinks  In the 1st pic the bog had dried sufficiently for me to remove the clamps. Doing this i found t was best to remove the clamps and wood guides BEFORE the Builders Bog had complelely dried, that way the paper came away easy without sticking to the Builders Bog. 2nd pic shows a section i did this way at the bottom front of the cab, dried and sanded smooth.

For the front section (3rd pic) which had pieces of ply completely gone i decided to cut and glue in a new piece (4th pic).