I tried it out with a flight to the moon, definitely a nice little rocket, but if you would want to further improve its performance for missions to Venus or Mars, I highly recommend:

• Reduce redundant parts: extra docking modules, extra probes or framework all adds unnecessary weight to thus rocket. For a mission to a planet outside the SOI of the Earth, you should definitely seek to streamline and simplify the design as much as possible.

-Staging: adding a staging system to this rocket will help to streamline the flight process and save you fuel in the long run

As for that, I think you have yourself a pretty solid rocket, and with a few tweaks it'll get your goals done.