I'll admit it - I cut a 6x6 fir post 7/8" too short. I don't relish buying a new one because of cost, it being the weekend, and the attachment to the base pier is with a knife-style simpson connection which took some time to get right. The fir is not pressure treated - it's an inside application. Can I safely cut a 7/8" slice off of the left over fir post and glue it in there with PL? The beam is being attached using 5" L brackets on either side.
If I was making a shim, I would not want the grain running the short way since it will tend to disintegrate under load and time. Ideally 7/8 plywood, partly because it is harder wood... otherwise plane or rip 2x6 or two 2x4s to the desired thickness, or 1x6 if the thickness will suffice. I would also glue and screw it.
Depends on 1) the amount of load on the beam/post and 2) how it’s loaded, (i.e.: uplift, lateral load, vertical load only, etc.)
1) You can’t use a post that’s too short if the connection is fully loaded. Connectors are designed with certain “edge distance clearances” , “end distance clearances”, etc. When the post is too short, it does not allow the connection to develop “full strength”.
2) I don’t think being 7/8” too close to the end of the post is important, unless there is a significant uplift.