Well, not homemade exactly. I'm trying to see if I can avoid the nearly $500 it will take to put Yakima crossbars and a regular tandem rack on my Sienna. I took an old Rocky Mount single rack that is designed for factory crossbars, spent $29 to get a second tray and bolted them together to make a tandem rack. The factory crossbars are spread as wide as possible which still leaves the rear tire of the tandem about 1 foot behind the rear crossbar. It feels fairly stable and secure but it is not completely rigid. There is some flex in the tray at the rear tire and some flex in the factory crossbar at the front fork so the assembly will flex back and forth a bit.
I think this is certainly adequate for around town emergency type use. I'm just wondering how well it will do for long distance road trips and what issues I should think about. Any opinions? Any cheap ideas for beefing it up?