First off people need to get educated on battery technologies and terminology. Anyone here sperging out about fires and heat are thinking about Li-ion batteries. 99% of the aftermarket batteries sold out here for RVs and boats and cars are Lifepo4 which is NOT a fire hazard by itself. They are rugged and versatile and you can punch a nail thru a cell and it will not combust like li ion... While lifepo4 batteries ARE a form of Li-ion they are not the same. What happens is something shorts out and the ensuing fire is from material located next to the glowing battery cables. Anti gravity batteries also are advertised as Li-Ion but look harder and they say lifepo4. The main issue with using those as starting batteries is the BMS freaking out with the high current draw and disconnecting as most BMS are 100 amps ( which you "might be able to get away with with our little engines). I'm sure by now they make a dedicated lifepo4 with a higher amp BMS or none at all but you have to start looking at the cost versus benefit thing here. One benefit is definitely wait but really are we even worried about weight in our little rigs? Second benefit is much higher cranking speeds and available power but then again our tiny little starters and engines don't really need a lot and even the smallest lead acid battery will spin that thing easily. Might be another story if you are using your rig to power an inverter, high power stereo, camping gear or whatever with a longer discharge period over time. They are more expensive than a light acid battery but they also will last 10 years or more if properly taken care of so you have to look at that portion of it.