diff --git a/src/app/shipyard/Calculations.js b/src/app/shipyard/Calculations.js
index b7a2f22a..dd381127 100644
--- a/src/app/shipyard/Calculations.js
+++ b/src/app/shipyard/Calculations.js
@@ -544,7 +544,7 @@ export function calcBoost(ship) {
   if (!ship.boostEnergy || !ship.standard[4] || !ship.standard[4].m) {
     return undefined;
   }
-  return ship.boostEnergy / ship.standard[4].m.engrate;
+  return ship.boostEnergy / ship.standard[4].m.getEnginesRechargeRate();
 }
 
 
@@ -585,7 +585,7 @@ export function armourMetrics(ship) {
       hullThermDmg = hullThermDmg * (1 - slot.m.getThermalResistance());
       hullCausDmg = hullCausDmg * (1 - slot.m.getCausticResistance());
     }
-    if (slot.m && slot.m.grp == 'mrp') {
+    if (slot.m && (slot.m.grp == 'mrp' || slot.m.grp == 'gmrp')) {
       moduleArmour += slot.m.getIntegrity();
       moduleProtection = moduleProtection * (1 - slot.m.getProtection());
     }
diff --git a/src/app/shipyard/Module.js b/src/app/shipyard/Module.js
index a8e5c3cd..afed8fae 100755
--- a/src/app/shipyard/Module.js
+++ b/src/app/shipyard/Module.js
@@ -150,10 +150,17 @@ export default class Module {
         }
         if (modValue) {
           if (modification.method === 'additive') {
+            // Resistance modding for hull reinforcement packages has additional
+            // diminishing returns implemented. The mod value gets lowered by
+            // the amount of base resistance the hrp has.
+            if (this.grp === 'hr' &&
+              (name === 'kinres' || name === 'thermres' || name === 'explres')) {
+                modValue = modValue * (1 - result);
+            }
             result = result + modValue;
           } else if (modification.method === 'overwrite') {
             result = modValue;
-          } else if (name === 'shieldboost') {
+          } else if (name === 'shieldboost' || name === 'hullboost') {
             result = (1 + result) * (1 + modValue) - 1;
           } else {
             result = result * (1 + modValue);
@@ -441,7 +448,8 @@ export default class Module {
     let result = 0;
     if (this['maxmass']) {
       result = this['maxmass'];
-      if (result) {
+      // max mass is only modified for non-shield boosters
+      if (result && this.grp !== 'sg') {
         let mult = this.getModValue('optmass') / 10000;
         if (mult) { result = result * (1 + mult); }
       }
diff --git a/src/app/shipyard/Ship.js b/src/app/shipyard/Ship.js
index 19bfdf64..87be0b90 100755
--- a/src/app/shipyard/Ship.js
+++ b/src/app/shipyard/Ship.js
@@ -937,7 +937,12 @@ export default class Ship {
     let epsChanged = n && n.getEps() || old && old.getEps();
     let hpsChanged = n && n.getHps() || old && old.getHps();
 
-    let armourChange = (slot === this.bulkheads) || (n && n.grp === 'hr') || (n && n.grp === 'ghrp') || (old && old.grp === 'hr') || (old && old.grp === 'ghrp') || (n && n.grp === 'mrp') || (old && old.grp === 'mrp') || (n && n.grp == 'mahr') || (old && old.grp == 'mahr');
+    let armourChange = (slot === this.bulkheads) ||
+      (n && n.grp === 'hr') || (old && old.grp === 'hr') ||
+      (n && n.grp === 'ghrp') || (old && old.grp === 'ghrp') ||
+      (n && n.grp == 'mahr') || (old && old.grp == 'mahr') ||
+      (n && n.grp === 'mrp') || (old && old.grp === 'mrp') ||
+      (n && n.grp === 'gmrp') || (old && old.grp == 'gmrp');
 
     let shieldChange = (n && n.grp === 'bsg') || (old && old.grp === 'bsg') || (n && n.grp === 'psg') || (old && old.grp === 'psg') || (n && n.grp === 'sg') || (old && old.grp === 'sg') || (n && n.grp === 'sb') || (old && old.grp === 'sb') || (old && old.grp === 'gsrp') || (n && n.grp === 'gsrp');