This is on near border line of use. but still you can check and optimize.. Like only load 2 ml of protein (instead of 2.5 ml) and elute in 3.5 ml buffer (little more diluted than 1.4 times as pr protocol). 

If that doesn't work you may try with a C18 spin column (this is what I would try first), it should be more efficient and you can concentrate your peptide if needed.

Sephadex G10 might be a better option

Thanks for suggestions currently I am using Amicon Ultra-15 of MWCO 3 kDa for concentration and dialysis of the affinity purified peptide of 9 kDa.