Millenium,
there are 3 common grips for the 2 hander
dominant hand / non dominant hand
conti / EFH : most common, easy to execute all variety of stroke, encourages early contact point. Should be hit with straight arms or slightly bent non- dominant arm
EBH / SWFH : more typical of clay courters looking for heavy spin, requires early contact and extended arms.
EFH / EFH : more common to ladies, usually those who learned as young girls with oversize (too heavy) racquets. Usually flatter stroke hit with later contact and little extension (as method to keep weight close to body). Usually hit with both arms bent (sometimes called "tree-hugger" style)
to answer your question, the grip position of the bottom hand in EFH will restrict the ability of the top hand to roll the racquet over the ball, therefore restricting the ability to get as much spin
you seem determined to want to hit with that grip, but why not use conti? do you just not want to change grips? Conti should be the most important grip you own so there is no point avoiding it.