Before I trimmed my bucket I aligned it all and kept it in place with painters tape. then drew the lines for trimming...and did a little at a time. Never trim before you know where to trim. You might be able to save it.
It's all up to you, if you build it yourself start where you want and ask us a lot of questions, that is why we are here.....and don't forget the big brown box shot. welcome trooper.