Second narrows is no biggie for a boat such as yours. We have been transiting the narrows in whatever boat we have had, for the last 25 years, at all states of current. When we had a 30 ft sailboat that would only do 5 knots, we paid a little more attention to the current, as we much preferred to go with the current than against it. In our present boat, we don't really need to check, but when we do, we try to gain some speed.
Sec Nar is one of the least turbulent narrows around,so the only real concern is your speed made good. If you can do 8 knots, you will always get through, sometimes with a boost, sometimes not.
You should monitor 12, as when a tanker is transiting the narrows, there is usually a call to clear the narrows until she passes.