If this were your only option I would advise using white rum rather than a darker-coloured variety if anything, but rum has a distinctive flavour and some of those aroma compounds may react with components of MHRB, whereas vodka is, by definition, neutral grain spirit, i.e. it has minimal levels of these 'congeners', so it's your call but I'd still recommend using vodka.

There's always the possibility I may have recalled the figures incorrectly, but the experiment was designed around commonly available kitchen equipment. After adding sufficient vodka to cover the bark with a generous layer of liquid, plus the subsequent rinses of the bark after the cooking process, the total amount of liquid collected was 300mL. More will have been used in the process because of evaporative losses and the amount that gets held up by the bark, The rinses are intended to improve recovery while minimising the overall volume of solvent used in comparison to a simple cook-and-filter process.

These details have not been finalised, hence the absence of a formal write-up. It would be fair to call this a work in progress, were it not on indefinite hold for the summer!