Pursuant to the invention, adapter blocks can be provided having a length dimension equal to the distance between hub axes of {TAIL ~ two connector elements} joined by a rod element of {HEAD ~ a selected length} 
Pursuant to the invention , adapter blocks can be provided having a length dimension equal to the distance between hub axes of { TAIL ~ two connector elements } joined by a rod element of { HEAD ~ a selected length }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD