I can't see it it's too small, but it doesn't matter because cpu overclocking has nothing to do with your ram.
hes running a first gen i5, cpu overclock as eveything to do with ram, hes changing the fsb not the multipier like on a second gen i5. since you already have your cpu overclocked and the ram is stabel you should be able to add the extra sticks to the MB since you are buying the same ram.
The only thing you need to watch out for is since you are populating all the ram slots you might need to add a little more voltage to the qpi/dram core voltage to make eveything stable. everthing might be fine but if you start having crashes/bsod then i would start by uping the qpi voltage