Well, the most obvious method would be to use less hops for your bittering charge, but this amendment would depend on the OG and the rest of the recipe design. The second would be to incorporate larger late boil or post-boil hop additions to offer smoother bitterness along with a perceived sweetness from all of those juicy/fruity flavors and aromas.
On more of a scientific level...
Vigorous and violent boiling of wort helps to coagulate unstable proteins. The harsh polyphenols in hops are very eagerly attracted to the non-coagulated protein which is present in the kettle during early boil. After a successful boil is complete, these proteins have binded with much of the polyphenols, and have become so heavy that they drop to form much of the trub you see in an IPA with a ton of kettle hops. Any polyphenol harshness sensed on the palate is likely due to: 1) transferring all of that trub to the primary, 2) poor hot break/insufficient rolling boil, and/or 3) boiling the hops for too long (one hour max). Boiling the hops longer than one hour will start generating sharp, undesirable and unpleasant flavors.
My suggestion is to allow the wort to boil for 15-30 minutes before even thinking about adding any hops. Tannins/polyphenols from the hops willl then be more effectively eliminated in the hot break. Once the hops are bound up with protein, there is much less surface area exposed, hence much less alpha acid to isomerize. The result is that you will have a smoother IPA with plenty of IBUs to combat the juicy late hops, but without any of that rough tannin harshness. Certain products like Clarity Ferm will help to prevent the precipitation of polyphenols and proteins by hydrolyzing the sensitive (haze-active) polypeptides in the region where such hydrogen bonding occurs. If you notice that your IPAs always struggle from chill haze, then making attempts to correct it will not only make your beer clearer, but it will cut down on much of that harsh astringency you sense as well.
There are so many variables at play here that can skew the results of tests like these. Even if the base recipe is the same and the only thing you're testing is FWH vs. Traditional Bitter, you still have to account for the amount of hops used, the age of the hops, whether the yeast choice or the grist is detracting enough to negate the subtle differences in hop character, the unique processes of the brewer, etc. Also, the judges/tasters for these at home tests are not always certified Cicerones. I work in the chef industry and my clients cannot discern a raspberry pie from a strawberry pie, or cod from haddock... I wouldn't be surprised if they couldn't distinguish a FWHd beer from one that was traditionally bittered. I would imagine that more often than not, they would have no clue.
