wrote:
Can anyone give me some ideas for temporary, but securable weight
ballasts?

I have seen specially shaped plastic bottles that are used for ground
vehicle weight testing. They can be filled with water, sand, shot, etc
to get the required weight. The bottle is shaped about like a seated
human, but with truncated arms and legs and no head - the neck is the
filler opening. The shape of the bottle allows it to be belted into a
vehicle using the standard seat belt. This is _not_ a crash test dummy -
it has no sensors and is not articulated. It's just a thick-walled
(polyethylene?) bottle.

Unfortunately I don't know the "official" name of this item and Google
isn't helping. These bottles get used a lot in vehicle testing, and
since you appear to be in Michigan, you might be able to ask someone
at one of the auto makers where they get theirs. Alternatively, you
might inquire at other places that do vehicle testing, like the auto
enthusiast magazines, Consumers Union (Consumer Reports magazine), etc.

You might be able to get smaller lead weights at a SCUBA shop. I think
they have a couple of styles: cast chunks of solid lead, and bags/pouches
that are meant to be filled with lead shot. Both styles will have
straps or provision for straps, so they should be relatively easy to
secure.

Matt Roberds