Thanks Muddy, these are the reasons my Grandson and I got rid of all tender or all none engine driven trains no matter who made them or whether they were Tomas & Friends characters or normal models of real trains. Our trains were always derailing especially at the top of slopes and at switch points. We were tired of chasing down derailed engines all around our spread out earliest of Layouts. I did find that adding weight to the engines did help to alleviate some of the derailments it wasn't enough to overcome our distaste for them and their odd tracking.
The Vicarage Orchard ~ Request Runs (Tender driven mayhem)