The Panasonic in my '99 100 is starting to fail, so it's time to look for a new battery. Has anyone managed to stuff a Group-31 size battery in the standard battery location? Odyssey has the PC2150. It's a Group-31 battery with great specs (on paper at least). It measures 13.0" L x 6.8" W x 9.4" H. The length and width look like they won't be a problem, but the height is very close. The 9.4" height includes the posts which are 0.882" high. A detailed drawing is on the Preliminary Specifications It has 3/8" stud posts so obviously some custom battery connectors and a custom holddown will be nessecary. Here are the Specs: 12 Volts 1090 CCA 1545 HCA 1370 MCA 100 AH at a 20 hour rate 95 AH at a 10 hour rate 200 Minute Reserve Capacity 13 Inches Long 6.8 Inches Wide 9.4 Inches Tall 75 Pounds 3/8" Stud Terminals 5000 Amp Short Circuit Current If the PC2150 doesn't fit, I'm sure the PC1700 will, but I'd rather have the larger battery if possible. I've also thought of the Lifeline AGM Marine battery or the Roll's flooded Marine battery, but the Odyssey seems like the best. My "dual battery" plan is to have the largest main battery as possible with deep cycle capability, and either a priority start or a small backup battery to self-jump start.