[mirtos]

Here is my shield bash and heavy shield, respectively.

  <thing id="wShldBash" name="Shield Bash" compset="Weapon">
    <tag group="wCritMin" tag="20"/>
    <tag group="wCritMult" tag="2"/>
    <tag group="wCategory" tag="Melee"/>
    <tag group="Helper" tag="Helper"/>
    <tag group="wType" tag="B"/>
    <tag group="wMain" tag="1d3_3"/>
    <tag group="wProfReq" tag="Martial"/>
    <eval phase="PreLevel" priority="10000"><![CDATA[~ If we are a heavy shield, we do 1d4 damage and one handed.
if (container.tagis[ShldClass.Heavy] <> 0) then
  perform delete[wMain.?]
  perform delete[wClass.?]
  perform delete[Helper.Finesse]
  perform assign[wMain.1d4_4]
  perform assign[wClass.OneHanded]
endif]]></eval>
    <exprreq message="Light Shield Proficiency required"><![CDATA[#hasfeat[fArmLgShld] + hero.tagis[Hero.ProfShield] <> 0]]></exprreq>
    </thing>

  <thing id="mShlHvSt2" name="Shield, Heavy Steel" description="You can&apos;t carry anything in your hand while using a Heavy Shield. You can Shield Bash with a heavy shield." compset="Armor" replaces="mShlHvStl">
    <fieldval field="gWeight" value="15"/>
    <fieldval field="gSizeCost" value="20"/>
    <tag group="mAC" tag="2" name="2" abbrev="2"/>
    <tag group="mArcFail" tag="15" name="15" abbrev="15"/>
    <tag group="mArmorChk" tag="2" name="2" abbrev="2"/>
    <tag group="mClass" tag="Shield" name="Shield" abbrev="Shield"/>
    <tag group="mMaxDex" tag="1000" name="1000" abbrev="1000"/>
    <tag group="EquipType" tag="Metal" name="Metal" abbrev="Metal"/>
    <tag group="ShldClass" tag="Heavy" name="Heavy Shield" abbrev="Heavy"/>
    <bootstrap thing="wShldBash">
      <autotag group="Helper" tag="Proficient"/>
      <autotag group="wClass" tag="OneHanded"/>
      </bootstrap>
    <eval phase="First"><![CDATA[~ Work out if we're equipped, or, if we're the child of a magic item, 
~ if our parent is equipped.
var result as number
result = field[gIsEquip].value
if (container.ishero = 0) then
  result += container.parent.field[gIsEquip].value
endif

~ If shield bash is being used, allow for use of shield and bash.
~ Remove shield AC if equipped, unless Improved Shield Bash exists.
if (result <> 0) then
  var ac as number
  if (container.ishero = 0) then
    if (container.parent.gizmo.child[wShldBash].field[gIsEquip].value <> 0) then
      perform hero.assign[Hero.ShldOffOK]
      if (#hasfeat[fImpShBash] = 0) then
        ac = container.parent.field[mAC].value + container.parent.field[BonEnhance].value
      endif
      hero.child[ArmorClass].field[tACShield].value -= ac
    elseif (container.parent.gizmo.child[wShldBash].field[wIs2nd].value <> 0) then
      perform hero.assign[Hero.ShldOffOK]
      if (#hasfeat[fImpShBash] = 0) then
        ac = container.parent.field[mAC].value + container.parent.field[BonEnhance].value
      endif
      hero.child[ArmorClass].field[tACShield].value -= ac
    endif
  elseif (hero.child[wShldBash].field[gIsEquip].value <> 0) then
    perform hero.assign[Hero.ShldOffOK]
    if (#hasfeat[fImpShBash] = 0) then
      ac = field[mAC].value
    endif
    hero.child[ArmorClass].field[tACShield].value -= ac
  elseif (hero.child[wShldBash].field[wIs2nd].value <> 0) then
    perform hero.assign[Hero.ShldOffOK]
    if (#hasfeat[fImpShBash] = 0) then
      ac = field[mAC].value
    endif
    hero.child[ArmorClass].field[tACShield].value -= ac
  endif
endif]]></eval>
    </thing>