"Shooting in the dark" - No pun intended, right? Seriously, Thanks for the prompt response. I've zipped the file (28MB), and just worked out how to post it. In case more information is helpful, here's some background. Hardware: I'm on a mid-2009 MacBook Pro (17"), 8GB (about 6GB free before loading XP), 500MB SSD. What I (think I) know: (1) To have backlighting, legacy instruments should be set to "additive", generics to "backlit" (2) instrument base layers are ambient/spot lighted, not affected by backlighting. (3) overlays should backlight - if they have a bus connection (always bus 1 on this model), and are set to operate through an available instrument rheostat (always pilot's knob 0 on this sim). (4) instrument base layers should be saved with alpha (in photoshop, saved for web with transparency), overlays should be flattened into a single background before saving. (5) there's a reported problem in XP10 affecting electrical system settings on imported models. The only issue I noted was that base voltage was down to "0", I set it to 31, matching the built in 172 in case XP instruments are 28V<?>, but it should be 14.5 on my plane. The change had no effect on lighting. BUT: (1) some dash-number overlays (like my airspeed and altimeter bugs) light up without _LIT versions, others don't. (2) some legacy/built-in instruments put in my panel "as is" backlight (like Turn Slip), others don't in my panel (like Airspeed). Are users expected to create and save _LIT layers for built-in instruments that work in their original models without them (or without them being visible)? Sim Notes FYI: there's an partial generic VSI above the left panel- done as a lighting experiment, hasn't worked yet. Also, there is a miniature autopilot LOC actuator just above the course selector on the HSI, this is a proxy for the GPSS select on the Aspen. Cessna 177RG Aspen.zip