Training and Living at Altitude (for 6 months)

JHow. I have adjusted my FTP for 7500 and go down to 5200 for intensity. The difference is 30-40 Watts going down to 5200. I did Mills Workout today and I had to adjust the FTP to my Lower Altitude FTP because the VO2 workout was too easy. So you use the same FTP at 10 as you do down at 5200?