Under assumption that Clan CASE is not supposed to be fitted to most C models, following GreekFire's example earlier:
Page 229, Atlas C record sheet:
Remove CASE from left and right torso
Adjust BV to 2232
Not errata. CASE remains per post here: https://bg.battletech.com/forums/errata/record-sheets-3050-upgrade-unabridged/msg1670146/#msg1670146
Wait - since when did Inner Sphere-based chassis be able to mount Clan-grade CASE with no tonnage or critical space requirement? TM p210 does not allow for this, thus the Atlas C described in the link here violates construction rules. As well as violating common sense - Clan-based mechs have CASE built-in to their frames but IS mechs do not: as a refit of an IS mech it would not magically gain the benefit of advanced Clan manufacturing techniques. Both BoT Supplemental and the RS:3050UU-IS errata are in error. If CASE is to be added it must follow the Inner Sphere construction rules, and that means one of the three heat sinks in the left torso must be lost to provide tonnage and critical space for it.
However, Battle of Twycross sourcebook page 49 describes the Atlas C changes (from AS7-D) as not having CASE of any kind. Thus, the RS:3055UU-IS errata and BoT Supplemental, if they should have CASE, are effectively introducing a second C model - with the Twycross model retroactively becoming C 2 unless errata is to be issued for that product as well to specify addition of CASE. I'm not sure that's the intent. Empyrus's "assumption" exactly matches to what FASA originally wrote 31 years ago. I don't believe his comments should be ignored/struck-through, but restored as valid errata, and the linked RS:3050UU errata is ignored/struck-through instead as its an illegal design.
Per Battle of Twycross, the only C model from that source that mounts CASE should be the Marauder C (page 48)
However, we didn't have a record sheet for Marauder C until BoT Supplemental (not that I'm aware of anyhow), and its got the same problem. The record sheet data sums to 75.5 tons when proper Inner Sphere-grade CASE is added.
Marauder C record sheet, page 185 actual (sheet 186 of 310 of PDF):
Recommendation: Remove the Heat Sink from the Center Torso. Add CASE to critical space in Left Torso. Mech remains half ton underweight. (Probably means BV comes down a bit due to less heat efficiency, too.)
I suppose something could be done with the armor as well, but as none of the other Clan Invasion IS-refit Cs adjust armor, this was the solution my group had used (though I'm sure we had a different idea on where to place the extra heat sinks)
