Its always a good idea to review a woodworking plan and double check the measurements. Then as you proceed through the measuring of the parts, take your time and double check again. Today I found an error in this plan. Its no big deal, an easy fix at this stage.
This is something that I have always advocated to a person building a woodworking plan. Take the time to read through the project building process to first get a general grasp of what is required. Then as you work through the measurements and parts, take your time and measure the parts out. If you find an error, contact the plan seller/designer to let them know. You will be helping out the next woodworker who decides to take on the same project.
The other bit of advice I would suggest is to build as you go, rather than cutting out all the parts, then gathering them up to assemble. Sometimes, materials you bought in your local area are not dimensionally the same as materials bought from the area the designer created the woodworking plan.