I'd actually be in favor of leaving the Tail Sweep off entirely. If you want to add a note that they get it when advancing to G, I won't object, though.
So how would you like to do the treasure?
Then let's add a note about advancement giving them tail sweep at Gargantuan size.
Strange that the treasure line gives them coins when the flavor text pretty explicitly says they don't. Well, let's say they accumulate treasure "less" than normal dragons but give them the treasure you suggest.
OK then. Are we settled on this?
Treasure: standard coins, double goods, triple items
Advanced Albino Wyrms
Albino wyrms of Gargantuan size or larger gain the Tail Sweep special attack.
ail Sweep (Ex): This special attack allows an albino wyrm of at least Gargantuan size to sweep with its tail as a standard action. The sweep affects a half-circle with a radius of 30 feet (or 40 feet for a Colossal wyrm), extending from an intersection on the edge of the wyrm’s space in any direction. Creatures within the swept area are affected if they are four or more size categories smaller than the wyrm. A tail sweep automatically deals the 2d6 hp damage (2d8 for a Colossal wyrm) plus 1-1/2 times the wyrm’s Strength bonus (round down). Affected creatures can attempt Reflex saves to take half damage (the save DC is Strength-based).
The only change I made from the true dragon is to make the DC Str rather than Con based. Do you think we should change that back?
OK, fair enough. Do you want to update with CR, treasure, advancement, the underbar, and anything else I've forgotten?
OK, I'll go along with that. But the tail sweep in the regular combat section needs to disappear.
I think you can remove the red question marks.
Tactics: breath weapon, then melee? Swallow whoever it can? A bit reckless but not stupid?