My PA is a couple of years older than yours (so it may be different), but my house batteries are mounted in a sliding tray (with little clips on each side) and my chassis battery has enough room above it to loosen the battery clamp nut then use a flat blade screwdriver to spread the clamp and loosen it. Just remember to remove the negative terminal first in case your wrench hits the top of the battery area while turning it so you won't cause a short and some fireworks...
Dave RVM#66 and Carol
1998 Pace Arrow Vision
Seeing the USA - 200 miles at a time