Can you brew a partial Smash?

Too much crystal obscures the hops. The sweetness hides the bitterness. The crystal malt flavors, such as caramel in light malts and raisin in dark malts, hide the hop flavor/aroma. I am not a crystal malt hater, but they can be overdone, and that is especially true for IPAs. In general, I do not make a recipe that has more than 1 pound of crystal per 5 gallons unless I really trust the source. More typically, I use 0-0.75 lbs per 5 gallon batch.

 

An add on to what Peter posted above. The type of crystal malt used will impact the overall IPA flavor profile. I do use 1 lb. of crystal malt when I homebrew IPAs but I use Briess 20L crystal and the flavor impacts that that particular crystal malt is more subtle.

Cheers!