December 2019: You can do a faster even better build of your own RSD-15 or RSD-7 nowadays, using Dirk Jan Blikkendaal's (of The Netherlands) ATSF N Scale Models kit for the RSD-15, I have one of his conversion kits and can vouch for the quality, the good instructions, the well thought out method he provides. His kit well worth it: http://atsfnscalemodels.com/projects/rsd-15, rsd-7.html