Walthers Centerbeam Flats (HO Scale)

I bought a 3 pack at a show recently and they seem to be decent cars…but light. Any suggestions on how to weight them (w/o load)? There doesn’t seem to be any place to hide weights like on a boxcar or gon.

Go to the Walthers web site and look at the following Adair Shops items:

143-4409

143-4412

Jim Bernier