This work presents an optimization method aiming to maximize the surge impedance loading of bundled transmission lines. The iterative method, based on gradient optimization, changes, on each step, the conductors' position generating a new bundle configuration. Such configuration matches a change on bundles geometry by shifting conductors on the direction that leads to the maximum reduction of the objective function. Both the reduction of natural impedance and the optimization of conductor's superficial electric field are evaluated. The former seeks the increase of surge impedance loading actuating directly on the maximal surge impedance reduction path. The second acts on the uniformization of conductor's superficial electric field, whose upper bound is the main electromagnetic restriction on the surge impedance loading increase when designing transmission lines. The last one was most effective when bundle's expansion is allowed until superficial electric field reaches its limit, resulting in greatest natural power transmission lines, yet, leading to most expanded bundles.