yeah i ive been doing that but its been like 2-3 weeks since ie played offline so i cant remember how well it works lol. online is the worst i swear they can just dash again
His F+4 is 10 frames. Reptile's Dash is -15 on block. Online, however, which I find myself in this situation most often, I just go for a trap or something instead of trying to get a guaranteed combo.
I personally opt for b121~gs, it's a frame fast than f4. It can be hard to react to a blocked dash, especially up close and I've had more success with b1 than f4.