I had a huge weight that came out of an old IBM mainframe disk drive (think 1980). Well, it was compact - about the size of a concrete block, cubed - but it weighed at least 75 lbs, if not more.
In the winter I had a full size car battery over there with long cables that came over and hooked up in parallel to my bike battery. That gave me some ballast and ensured easy starts at 8 in the morning when I was leaving work.
One of the fun aspects of sidecaring is all of the exaggerated body english one uses in driving. Lets assume we are driving a rig set up for USA roads:
with the sidecar mounted on the right, when you go around a left turn, you need to hang off to the left of the bike as much as possible to unload the sidecar wheel, because that is where the weight is going.
Around a right hand turn, and it is a totally different story. The sidecar wants to rise up as the weight on the vehicle is transmitted to the left.
The "weight" is always transmitted to the side opposite the turn. Think of a bread truck in a turn. The top leans opposite.
So on a right-hand turn, I always took my right foot off of the foot peg and put it on the sidecar frame and leaned as far into the sidecar as I could, in an effort to keep the sidecar wheel planted.
Under normal circumstances, you will slow the vehicle enough so that you don't lift the wheel, but after a while you learn where that "edge" is. Great fun.
And then there is the 'S' curve!
I found that if I lifted the sidecar on my way into a S curve, I could pilot the rig all the way through as if it were a 2 wheel motorcycle - which it was, albiet with a huge growth on one side.
And that was just one little piece of road in my neighborhood that ran alongside the interstate. It didn't get much traffic and I certainly didn't make a habit of these stunts. (But snow is a BLAST!!!