Originally Posted by corners
If it's one layer then it's between 3 and 5 grams. P1 has written on these boards that the lead is there to match the frames. If these are "retail" (but hand-chosen) US K90s then the total swingweight would end up around 350, which is what the poster Art Art has reported several times for Fed's sticks measured at tournaments.
One would think that a USK90 + 3-5 grams of lead, + heavy strings (gut + lux = 17 grams) + overgrip + stringsavers&powerpads would total more than 364 grams, but remember that these are hand-chosen frames and might be selected for being a little lighter than average. P1's custom handles might be lighter weight than stock PU handles as well.
I'm not questioning the weight, just Edberg make it seem like there's a lot of lead on the head, which isn't true like you said. they are just there to match to specs of older racquets. And if Sampras can swing a PS85 with 3-4 layers of lead at 3 and 9, I'm sure Fed have no problem swinging a 6.1 90 with a few grams of lead.