What are the extra bolt holes under the frame by the back tire for on the radrover 6+ step through
They are for 5 x 0.80 mm bolts. ::)
Actually....I don't know their purpose, but in the production world I often saw "jigging" equipment that was used to perfectly locate components during weld manufacture. Seeing that there are three holes on each lug, I would suspect they are manufacturing aid. Precision bolt up makes for better quality manufacture.
In the auto factories I have seen things such as "complete engine assembly" spray painted off-color to identify it as "fit test component" (and not to be moved or modified).
The important part of this message is DO NOT use them for mounting accessory loads, etc. Jig equipment is used at points not necessarily intended for high load, to be sure that "deep weld" areas are not susceptible to excess heat outflow, during the build process.
The world sure has become complicated!