'Full sun' is relative :-) Full sun in your Maine location is not going to be the same as full sun in Texas or California. Because you are so far north, the angle of the sun is lower and the heat, even in summer, is not so intense......pretty similar to my own location. And most JM's, with the exceptions of those with variegated, very pale or reticulated foliage, will grow fine in full sun here.

'Shaina' has a reputation for being both very sun and heat tolerant and is recommended for these situations in climates more intense than yours, so there should be no problem with it, all other factors being equal. Wind is another issue altogether. I would not recommend any JM for a high wind situation - the foliage is too fragile and buds too susceptible to freeze damage from cold winds in spring. A sheltered location - out of the wind - but in full sun should be fine.

My Shaina has been in full sun since early spring and is simply gorgeous right now! I live in the Pacific Northwest, and the tree is in a large ceramic pot sitting on a wheeled dolly so I can move it around a concrete-floored patio. Last year I had the tree in a shadier spot and the colors weren't so bright, but this year it's been nothing but happy, happy, happy where it is - in full sun, turned every so often so that all sides get a roughly even amount of sun. I wish I knew how to attach a picture, since I just took one this morning because it is so beautiful.