11" Twist too slow?

[User4302021]

I regularly shoot 210 SMK's at sea level out to 1,200 yards with an 11 twist (2,900 fps). I have taken them to 1,500 yards, but I feel they start to get wobbly out in that range.

Since I plan to use this rifle as an ELR trainer, I am rebarreling it with a 28", 9.5 twist Benchmark.