GPU #0 = Sapphire AMD Radeon R9 280X VAPOR-X 3GB
GPU #1 = RADEON R9 290 4GB POWERCOLOR PCS
When I run Claymore 8, I just noticed this come up
Cards available: 2
GPU #0: name: Tahiti, 3072 MB available, 32 units
GPU #1: name: Hawaii, 3072 MB available, 40 units
Total cards: 2
It's ok, for 4GB cards OpenCL allows 3GB only for using.
If v8 is slower than v7 for 290 card, try HashCnt = 1280 for it, for your system with GPU #0 280x and GPU #1 290 it is "-h 896,1280".
The cards are using ~1GIG less memory than what it shows Claymore has available to it.