A guy named "lonestar_tx" from Reddit posted a brick built cross using flex track. It's one of the best I've seen and costs under $10 USD
It seems to be a very stable design and finally puts those ugly "flexi-tracks" to good use. Check it out!
LINK: Video Brick Built Power Functions Cross Track
LINK: Download building instructions (LEGO Digital Designer)
Original post: https://www.reddit.com/r/lego/comments/5i40y4/brick_built_power_functions_cross_track_video_ldd/