My understanding is that you'd want the head to only make contact with the lands. Or very minimal with grooves. Measuring both would give you an idea.... As always, field results trump everything else.
you need to think outside the pellet for real accuracy .. thats my concensus lol ... pellets generally size themselves in the barrel as long as they arnt grossly loose .. what happens when they exit the barrel is where i think the real meat and potatoes are lol ... they need to stabilize quick right out of the muzzle ..