For a sign that is 40 feet away from viewing p10 panels would be fine, here is a howto done by ryanschristmaslights in South Australia.
i have same power source etc but only 2x1 p10, but double sided so people can see from either direction, works fine, only require to recharge battery every 4 th day
https://auschristmaslighting.com/media/adelaide-mini-2017-battery-powered-tune-to-matrix.245/
hope this helps cheers Boof63