I wouldn't be too worried about the seams on the Under Armour. They never bothered Leah.
Gayle, age 45
Boston brace as a teen for AIS
Oct. 2010 fusion T8-sacrum w/ pelvic fixation, TLIF at L4/5.
Feb 2012 major A/P revision for broken rods
mom of Leah, 11 y/o, diagnosed Jan '08 with 26* thoracic JIS (age 6)
4/08 26 degrees, brace 16 hrs/day
9/08 17 deg. OOB - brace discontinued
9/09 30 deg, resuming Boston brace
5/2010 VBS Dr Luhmann Shriners St Louis
5/2012 stable 2 yrs post-op, ~12 degrees
also mom of Torrey, 8 y/o son, ~15* T