My dad had a cayman S for 4 years it was only taxed April to October. We had it on a trickle charger but on most sports car the battery is flat after about 10 days mini should be OK I would suggest starting and letting it warm up at least once a month I usually took it out of the garage and let it run while washing the car gave it a chance to warm up and made sure it was always clean when had it under a cover inside the garage silica gel is probably a good idea. We never over inflated the tyres just kept an eye on them hand brake we left off and left the car in gear

Hope that helps