It is less than half [2/5 and 3/5, IIRC], but Yes there is a 2G-5G 'flip-flop' coupon design listed in ASM IX. And it gives an 'All Positions' welder qual.
Welder can be tested in 2G and 5G position on same pipe coupon provided the following requirements are met
1. Coupon diameter shall be minimum 6" NPS
2. A total of 6 nos. bend test specimen are required (for mechanical tests)
3. Use figure QW-462.3(f) for dis 10" NPS or larger and QW-462.3(g) for 6" NPS and 8" NPS
Welder so tested can be qualified for all positions and for outside dia above 2-⅞".