stalled out batch

So I have a batch of Smoked Porter that I started a few weeks ago - OG of 1.064 and its stalled out at 1.030. I was using Safale US-05 American Ale (surprisingly the first time I actually made a starter and its stalled out).

I have a spare package of Nottingham sitting around...would I severely alter the taste by mixing yeasts? Any reason I shouldnt use the pack to try and get it down to the 1.016-1.020 I was aiming for?

HELP!

My LBHS was out of Nottingham one time and they recommended S-05 as a substitute, fwiw. It'll probably taste fine.