The powder's Australian manufacturer Thales-ADI produces comprehensive load data for what it sells as 'Bench Mark 8208' in its home country. This includes 6mmBR. The ADI guide is more comprehensive than Hodgdon's data for 8208 XBR and is a useful supplement to that. Here's what it says:
6mm BR Remington
55 Bench Mark 8208 30.0 3204 33,900 cup 33.5C 3546 44,800 cup
58 Bench Mark 8208 30.0 3207 36,800 cup 33.5C 3552 50,000 cup
60 Bench Mark 8208 29.0 3121 36,800 cup 32.7 3475 48,900 cup
65 Bench Mark 8208 29.0 3084 36,300 cup 32.3 3397 48,700 cup
70 Bench Mark 8208 29.5 3045 37,100 cup 32.7 3361 51,600 cup
75 Bench Mark 8208 28.0 2926 38,900 cup 30.8 3167 48,800 cup
80 Bench Mark 8208 27.0 2823 39,800 cup 30.4 3107 49,500 cup
85 Bench Mark 8208 27.0 2782 41,400 cup 29.8 3016 49,900 cup
90 Bench Mark 8208 25.0 2599 41,500 cup 28.0 2813 50,000 cup
100 Bench Mark 8208 24.0 2388 40,500 cup 27.0 2630 49,800 cup
107 Bench Mark 8208 24.0 2380 42,700 cup 26.7 2555 50,400 cup
Being 6mm BR Remington, it'll be the short throat 2.2-something inch COAL version, and a long Norma or custom throat will allow higher charges. The fact that ADI publishes 8208 data for the cartridge with 90-107gn bullets tells you something though - that it is worth trying.