I took some more measurements and I was wrong--a group 41 battery will fit,
once the seat is out of the way.  I measured ~6.75" high, ~7.25" wide
(front to back) and  ~13" long.  A standard 41 is 11.5" long, 6-7/8" wide
and 6-5/8" high.    I will be leaving my extra battery under the rear seat,
however.  I do need to fix up those swivel seat mechanisms....   One of VWs
finest engineering designs.

                                                        Jay