It should work just fine with PTT keying I used a Tokyo Hy-Power HL-50B for a while with mine, no issues at all, you might have manually switch bands until you get all the auto band switching sorted out.
I have one and it works great. But you have to e careful to not overload the input. I use 2 to 3 watts input from my Flex 1500 and monitor the output and swr carefully so as not to exceed 50 Watts. PTT quit working but I find that COR works fine on the Flex. Keith W7ZAC