Thought I would share a quick technique I have used for years to get stiff vinyl tracks to sag. I am working on an old Italeria T-34 and the tracks are a nightmare. I tried to glue them to the roadwheels with CA and failed three times. So I went old school. Drill a hole in the side of the hull where you want the tracks to lay against the tops of the roadwheels. Straighten a section of paperclip and stick it through the hole, over the tracks. Prop up the inside end of the paperclip with a chunk of sprue and CA the heck out of it. Once you put the upper hull on, with the fenders, you really have to look for the paperclips.
Granted, if you are going to take the model to a contest you will want to pitch the vinyl tracks and buy AM tracks. But, if you are building for a diorama or just for fun this tip might come in handy.
Shaun