I have try placing both sub in front..............by right should feel more bass but don't turn out that with both sub blasting, it sort of create a 'numb' area ie both sound wave cancel out each other, out of phase which I discovered using a spl meter. Yes I can use the phase to adjust it but the effect is still not so good.
So now I am using one sub front left & one sub rear right. U have to make sure that both sub output at the same level & have to fine tune the phase on the sub using spl meter. Only disadvantage is having to use very long sub cable. In my case use one 3m & 10m QED sub cable.

Having a 7.2 set up is very syok! LFE is very syok & even my ball get pounded!!!