If you do want to go lighter battery, I would suggest you try Antigravity batteries
I have had one on my 625SXC for 18months and it is excellent. In the cold weather the starting warms the battery up so by 2nd or 3rd try they turn over normally. mine will start down to about 5 degrees C easily.
he is an inmate here as well. (usual disclaimer - no connection just happy customer yadayada)