yes, ive sometimes replaced bits if i see a weak point when assembling. i only do kits, predominantly grand prix bikes by tamiya. i have also made scale bits like connectors/tools and steering dampers that are linked to the forks rather than a static plastic bit that comes with the kit. the brass tube in the same scale as the plastic for example looks like anodised alloy, not like painted plastic. ill have to post a pic or two.