I don´t have really poor fps with the Viper but i have less fps with the Viper (on the ground) than with the Hornet for sure. The odd is, i get stutters when inside hangars at Incirlik AFB in Syiria map.
Although is not a big issue for me because i get good performance but it´s noticeable.
I´m getting great performance with the Hornet.
I7 4790K 4.4ghz, 32 Ram, GTX 1080ti, SSD´s, and Valve Index at 120hz refresh rate.
SteamVR IPD 1.0 (default) and DCS PD at 1.5