.... because this thing makes parts fall off. at 41% efficiency, this thing is a nightmare. Verdict is still out on the XL, but for now, if you play like a heavy, you shouldn't have too many problems. The speed allows you to get in and get out without too much trouble and the cooldown from those 21 heatsinks lets you baseline pretty fast and blow more parts off...
5/5, Classic Zeus build. Replace the MLs with ERMLs and the XL with a light engine and it might work even better now. Endosteel upgrade, LE335, ERML upgrade, one fewer heatsinks, tracking computer and a few points of armor off the shield arm to make up for the remaining single crit slot and spare weight. Nearly as fast as the XL because of the endosteel weight savings, and considerably more survivable.
And here is an LE310 alternative that gets you back to 21 heatsinks and full armor (by using light ferro armor).