The frame conversion kits are simply to be used while your bees transfer to the langstroth frames you supply for them - so a means of fitting smaller frames into a bigger box. Never used one; bound to be fiddly at the start; need to practise before doing the job; remove bees from comb fit extensions and replace. Likely only five to do, anyway. Either choose a warm day, or be quick, to prevent brood chilling.
I would maybe make my own, but more likely to drop in a couple of 47mm thick timber, the width of the nuc, on which to lodge the frames temporarily.
The kits have two purposes. To hold the frames in position and to reduce extra comb being built by the bees and bracing them securely to the sides and each other (wasted work for your new nuc as well!).
Regards, RAB