Re: Winter Storage
Strongly suggest storing with top up .... Folds and creases can really seem like they're permanent and noticeable. Also ... the seal to the back window is held together tightly. Keep the windows closed also .....
The "float charger" style battery tender should be hooked up to the battery with the cables connected. It will keep all your systems at ready, and keep the battery topped up without cooking it, as regular chargers will. If you only plan to have it in storage for about 4 months (as you stated), I wouldn't worry about starting it up at all, unless it is stored outside exposed to severe cold and such. In a garage, don't bother for just 4 months. Should be fine.
Tires ... maybe up to 40 lbs, to help with "flat" spots.
I use tennis ***** in the muffler tips to prevent mice from going in, and put about 6 bounce fabric softener sheets in the car on the rugs. Some have said this prevents mice inside also, but it makes the car smell nice when opening it in spring. I really don't think dessicant packs in a roadster are needed, because the top and cover should breathe out any "moisture" build up inside.
Just my $.02