The group 24 AGM battery (50 lbs) in my new-to-me 2014 Suncat had to be replaced. I have never been a fan of Lithium batteries because of the cost but, times have changed. LiTime had their 100 AH "size" group 24 batteries (15 lbs) on sale for $189. That is not far from what I would have paid for a good AGM replacement.
So, the new battery fit nicely in the existing tray and tie-down, and, I rid the boat of 35 lbs! 35 lbs is a lot for a 17 foot sailboat.
I know 100 AH is a lot for a Suncat. But, I also know from experience power consumption can creep up on you as new things are added. Now I won't worry much about it.
I replaced the 2-120AH wet cell deep cycle batteries this year with a lithium 100AH. Like you stated, the weight savings is incredible. So much easier installing it. I'm also going to install a solar panel and charge controller. With the lighter weight, I may move it farther forward in the cabin.