slideshow using epson projector, & iphoto

Prior to Mavericks and Yosemite, I had no problem using my MBP 2011 to do a slideshow using an epson projector. Now I cannot seem to make the projected picture the correct size, and sometimes the row of photos for the slideshow that appears above the current photo, also is projected. When the photo is projected to big, the edges are cut off and so is access to the slideshow controls at the bottom of the screen.

I used to go to System Prefs > Displays and choose 800x600, and Mirror displays. This doesn't work now, neither did other screen size choices.

The mac is recognizing the projector, and I have the setting "optimize for Epson" chosen.

The epson is at my branch library where the slideshow is to take place; spent an hour there yesterday to no avail. Now at home I don't see the same choices in System Prefs > Displays but hope someone can give me some advice to try when I go back there tomorrow. Thanks!

(Rather not use the new Photos because it makes my MBP overheat with fans blasting loudly.)

2011 MBP 15" Yosemite 10.10.5

Thanks!