Leaving a gap between the modules can be risky. A 1HP blank panel from Doepfer costs around 3€. Much cheaper than damage caused by a short circuit due to an involuntary intrusion.
The 2hp drum modules are of good quality. Richard Devine’s Current Live Setup features a 2hp Kick and a 2hp Hat:
An attenuverter will allow you to adjust (reduce or increase) the amount of modulation you wish on the tone or the decay of your 2hp Kick, for example. This is an essential tool. The most complete modules have an attenuver for each of their main cv inputs.
We often suggest a utility module like the 3x MIA: it contains an attenuverter function (among many others). You will be able to dose the modulations reducing the width of an lfo or a random, and this module can even mix several modulations together.
'On ne devrait jamais quitter Montauban' (Fernand Naudin).