All I can suggest is that in order to balance your campaign, simply compare the ACTIVE COST of an attack versus that of a defense. They should be approximate. A 6D6K attack is 90 Active Points. 15PD/ED Resistant Defense Armor is only about 45 Points. Your attack is TWICE as powerful as the armor.
And even at that, 90 Active Point armor would yield 30PD/ED, which works out to about 30 STUN getting through the armor, so it's likely to STUN just about anyone wearing such heavy-duty armor. Of course, a Ship's guns should sting the best armored character (at least in a non-superheroic game).
This comparison works better on lower levels. A 6D6 EB would do 6 BODY/ 21 STUN on the average, and be about 30 Active Points. Equivalent Defense would be 15PD/ED (Non-resistant). You'd do about 6 Stun on a hit, which would sting but would not disable the guy. A really good hit might have more impact, a low damage roll being all but ignored as a glancing wound.