Houston....We have a problem

[Licensed to kill]

I bought the top and side wood kits for my 31 Deluxe delivery but made the bottom wood since it seemed pretty simple. Put all the wood together, everything went together quite well until I went to start fitting the quarter panels and they don't fit. When I clamp the back of the panel to the door posts at the back, the front of the panel is 1" short of fitting to the front of the front door posts. In other words, the wood frame appears to be 1" too long. However, the floor that I made is exactly the same length of as the original and the brackets front and back can not be adjusted for the discrepancy. As you can see in the first pic, the panel fits OK at the back door post, second pic shows that the holes for the carriage bolts do NOT line up with the wood brace about half way down the length suggesting that the issue is between that brace and the rear door posts, the third pic shows that the floor is exactly the same length as the original and the last pic shows how short I am from the panel fitting the front of the front door post. I am at a loss as to what the cause is and therefore have no clue how to fix it. Suggestions??. I can provide any pics that may help.