If you actually read the wording of the abilities, though, they don't stack is the point. It's a logical houserule (and might actually make Monkey Grip useful, because it sucks normally), but it doesn't actually work. Even that quoted line says 'in many ways', and the next two lines explain exactly how...you count as one size larger for size checks, and can wield weapons larger than normal - in a separate clause from the 'you count as larger' part.<br/><br/><div class="quoteheader"><div class="topslice_quote">Quote</div></div><blockquote class="bbc_standard_quote">With powerful build for all purposes you are one size larger.<br/></blockquote><div class="quotefooter"><div class="botslice_quote"></div></div>If you read Powerful build, that's not true, which is the problem.<br/><br/><div class="quoteheader"><div class="topslice_quote">Quote</div></div><blockquote class="bbc_standard_quote"> That means that when you use two weapon fighting you can have a two handed weapon in your main hand and a one handed weapon in your off hand. However monkey grip is only for you main hand which makes it so you would have a two handed weapon in your main hand and still need a light weapon in your off hand.<br/></blockquote><div class="quotefooter"><div class="botslice_quote"></div></div>And this is explicitly not true for Monkey Grip. A two-handed weapon still requires two hands to wield, it says so in the second line of the ability.