It's possible to put any kind of grip on any bow, but a straight ASL grip probably isn't the best fit for a moderate r/d bow. You'll notice that the riser of a moderate r/d bow begins to deflex before it reaches the end of the fade outs. That's not the case with an ASL handle, which is straight to at least the end of the fade outs before the limbs start a gentle curve toward the back (back set) or belly (string follow).
Too, most r/d bows are 1 1/4 to 1 3/8 inches wide at the fade outs, compared to about an inch for a typical ASL. So, putting a 2-inch straight grip on a bow width that starts at 1 1/4 to 1 3/8 inches would yield a very large circumference grip. And, thinning the grip area down a bunch might look a bit weird.
Of course, you can construct the 2-inch deep straight grip on a deflexed riser. Haven't seen it done, but I'm sure someone has tried it. Would like to see what it looks like.