Maximum printable size isn't an easy question to answer. It has more to do with maximum cured area per layer.
I would say the max solid object for a non-tilting resin printer is probably about 20mm x 20mm in the x/y ... so 400mm^2 you can distribute those 400mm^2 however you like in x/y in the build area. Hollow models will have much less cured area per layer than a solid model, so you could print larger hollow models.
In the extreme case of a honeycomb hollowed cube, you could print the full 60x40 x/y size.
Adding tilt to the LittleRP doesn't increase the build volume, but increases the cured area you can have per layer, potentially up to 100%.