What
SFSAbhishek is trying to say, is that if your engines are stretched so that they produce 2x thrust while consuming the same fuel, the isp is unrealistically higher. Which means unrealistically higher dV.
We wouldn't be talking about this if you were to put a bunch of stock engines on the bottom until the necessary TWR is reached.
if it can't reach orbit in that state, just add more fuel and one or two more engines.
Respect physics!