"Acer Extenza" doesn't tell me too much about the unit's spec's, but you asked the right question: "Am I risking more than boot failure?"
Generally, no. I'd insert one stick of RAM, turn the unit on and go into BIOS mode (SETUP) and see if that works. If so, then shut the system down again and insert 2nd stick.
I would Google the specific Acer Extenza model and see if I could find the voltage and CAS ratings for the memory, or look at the existing memory and see if some "1.v" voltage is specified and a "C" value is specified. If that matches the new stuff, you're probably fine. "Heat" and "Voltage" are the biggest concerns with laptops.
I think you'll want to do all of this without the battery being installed, by the way. Remove that and then do all disassembly and inserts.