your mini if ya could call it that, more of, the project you have isnt a 4r2 in that sense.
the pic ya posted was taken by me, and it is a minus derived yes, but used MANY more minus/mini things that yours, as in didnt have a 'space frame' it was a front subframe that was mounted at the rear ...
(still had a front sufram just no engine, all inside/flor etc were mini/minus, just the back and had vent/kit things for ventilation of the rear engine (a series by the way)
plus this one is/was only a replica 42r. as they were/are originaly metroracers so ive learnt since ???? again n0t 100% there
yours yes is as the very basic level formed from a minus .. that is the shell (roof and sides) are made from/with minus, but thats were it ends ! ..
all the front end (removable) and rear all the insides and floor just is'nt mini, nor minus related ....