3.5 V is a reasonable setting for an ESC LVC if a little low. You have to keep in mind that the resting voltage is always higher than the loaded voltage. The ESC will respond to the loaded voltage. If you set your LVC for 3.5, you might find the voltage is higher when you stop and measure it.

Another approach is to set your LVC lower, like around 3.3V but use an alarm like this one.
https://hobbyking.com/en_us/hobbykin...B&gclsrc=aw.ds

You can set it by .1V to start beeping. You need to be running a battery with a balance connector to use this. I have my Losi SCBE setup this way. It is set to 3.6V and my LVC is at 3.3. I stop to recharge when I hear the beeping. It will be intermittent at first, kicking in during moments of high load and then then stop as the battery recovers. This gives you a "soft" warning when your battery starts to get low.