The remaining deviations from a perfect cylinder are within tolerances to create photonic crystals with high reflectance and a well defined photonic band gap. The somewhat shorter length is remains sufficient for our applications and may be further improved by increasing the number cycles, although doing so would require further optimisation. The current optimisation has been achieved by manipulation of multiple etch parameters and moving from a 2-step process to a 3-step DREM Bosch process. In future work the 3-step process could be further improved by the use of a gas which is chemically inert with respect to silicon, such as argon, to ensure removal of the fluorocarbon but no chemical etching of the silicon, thus truly decoupling the removal and etch steps. The ability to exponentially ramp parameters, instead of linearly, would also give more freedom. We foresee that moving to a 4-step DREAM (deposit, remove, etch, ash, multistep) process with added oxygen plasma step to further protect the walls by formation of a silicon oxide layer, may also offer more avenues of to improve and expand the reactive ion etching of nanostructures even further.