i've got one in mind i haven't started yet, but might give you some ideas
i was walking thru my local machine shop's scrap yard and found a pc of 3" thick X 17" X 14" steel - rough torch on two sides - didn't cost me a thing, and it weighs 157 lbs - i'm going to clean it up some cutting the two rough sides and reducing to approx 15 X 12 but figure i'll still have 120+ lbs in wgt
going to mount it behind transaxle vertically, hinged at the bottom end on two 3/4" pins, but make it so it would normally stay in vertical position, and if i needed more wgt, i can swing top end down to create a shelf to put more wgt on top
doubt i'll need it but in case, it'll be ready