41999 buggy motor conversion

Thanks to rebrickable, I built model 41999 from the parts I have in my collection, but it is definitely too weak on L motors. I found a conversion to a buggy motor, but it requires a 1x13 gear rack. I don't have such a part, and the model uses 1x7 gear racks. Is there a clever way to use 1x7 instead of 1x13? Here is a link to the conversion submitted by /u/DynamicznyDexter [link] [comments]