Replacing post caps on deck (Not really woodworking, but it's close enough)

So the post caps that were installed on my deck 10 years ago, are garbage. Cheap plastic, that were already deteriorating 2 years in. One of those projects that needs to be done, but gets pushed back. So started tackling it recently. Was going to build my own, but the pressure treated ones at HD were surprisingly decent, and since these will be painted anyway decided to buy instead of build. Saved me a ton of time. So finished them with 3 coats of Sherwin Williams exterior SuperPaint, and 2 coats of Total Boat Halcyon. Will be interesting to see how these hold up. One of my challenges is that the posts are not a standard 4×4 or 6×6 size, since they are 4×4’s wrapped with Trex (generic HD equivalent). So the outside dimension is 5×5. So, using the 6×6 size post caps from HD, I had to make 1/4” shims on each inside face to fill it out. I’m attaching these with some construction adhesive on the top of the post and then 16 gauge nails on all sides. So far seems to be working as expected:

The next hurdle, which I new about is that the builder didn’t cut all the posts evenly at the top. So I’m going to have to fix some of those. Here is an example:

OK, so the bottom caps had gone on fine, no issues, but when I took off the ones at the top of the deck I found this:

So there is no wood to shoot the nails into. I can deal with this, was just unexpected. Really have no idea, why he cut these short, when the first 2 were not. So need to get some 4×4 tomorrow to fill these gaps. So hopefully tomorrow I can get all this done. Thanks for listening.

-- Chris, Pennsylvania