Scratch-built doesn't mean the entire thing needs to be custom designed and built! I would simply use a proven suspension design off of another car and develop new parts around those suspension pieces, and integrate belt-drive stuff. Much easier that way
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SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz