Here’s another solution I use for mounting the MFJ antenna: 2 pieces of PVC pipe. The telescopic whip is carried inside the smaller diameter piece with caps on each end to protect the whip. The small diameter pipe fits inside the large diameter pipe which also has end caps on it. A reducer coupler connects one end of the small diameter pipe with one end of the large diameter pipe. The antenna is mounted to an end cap which has been drilled for a stud mount.
My counterpoise is a wire with quarter wave links for each band.
Paul K9PM