It is all relative, hopefulnovice. Depends on when those four hours of sun occur. For example, late afternoon may be too hot; 7am-11pm would be fine. Sun exposure slightly longer than 12pm would be fine in MD. Down here though, I have to monitor the leaves after 11am-12pm to make sure they will be ok during the summer months; you are so much further north though, that you can give them more sun and get away with it. The only thing that might be "bad" is that Limelight has immature blooms. Immature blooms start green and the more exposure they get to the sun, the faster they turn white. The less exposure, the more time they remain greenish. If you wish the blooms to remain green longer, observe how they fare in this location next summer and how fast/slow they turn white.

I have mine in one hour morning sun but it is against a white wall in bright light---just really no direct sun except for that hour. They bloomed beautifully this year (until they were attacked by spider mites.) :( Lost 1/2 the leaves mid summer, but they are growing back and even rebloomed on the new growth.

Thank you both! I feel much encouraged now.