Fitting Metal with pie cuts

Hello All!  This is my first post here and I hope I am following the rules and participating correctly.  I've read most of this site and have found a few mentions of bending trim but not having good results.  Our camper is a 1970 Banner Reno-22'.  I had to rebuild the entire back end and one side of the frame as it was completely rotten from water damage.  After that, we put on brand new skin and PVC roof.  The skin went on pretty well and the roof turned out good too.  The problems we are having is getting the L trim to bend around the curves without buckling.  And after our first attempt, I'm embarrassed by the lame attempt at getting the siding joint to be covered properly by the trim.  We plan to remove all of this first attempt and redo it.  I'll post some pix and appreciate any pointers in what might be a good fix for this.  We have a few ideas but figured we'd ask the pros first!  Thanks much for any input.

www.facebook.com/Camper-Redo-1970-Banner-Reno-106686964886418/photos/pcb.143634464525001/143632684525179/


www.facebook.com/Camper-Redo-1970-Banner-Reno-106686964886418/photos/pcb.143634464525001/143632647858516/

www.facebook.com/Camper-Redo-1970-Banner-Reno-106686964886418/photos/pcb.143634464525001/143632784525169

www.facebook.com/Camper-Redo-1970-Banner-Reno-106686964886418/photos/pcb.143634464525001/143632751191839