I need some assistance: What are the biggest modern TFs with lower legs that retract in a sliding motion, covering up the upper leg? Think like: G1 Springer, Astrotrain, Hot Rod, Tracks etc? Sizewise I'm thinking Voyager to Ultra/Leader class. If there's not a suitable 'donor', how hard would it be to custom make legs like these? Suggestions as to how I'd go about it? Thanks!