I ultimately decided to replace the power connector with that of the C64 as well. This decision is backed by a few reasons:

• The C64 power supply outputs +5VDC directly, therefore we no longer need the TSR-2450 converter and all the filter caps and inductors, which I removed promptly. While the TSR-2450 is very efficient, it will still develop some heat and keeping that outside the unventilated body of the C16 can only be a good idea.
• The TSR-2450 is not exactly cheap (but I still love it!).
• The center-negative barrel connector is error-prone polarity-wise.
• Anybody interested in LittleSixteen surely has a decent C64 power supply already.
• It is easy to change the power supply with a beefier one, if needed.

This isn't all pros as it seems though, as we still need to provide the Motor pin of the Datassette connector with +9VDC, so how can we do that? We can just borrow something more from the Plus/4 which, despite using a different connector, is fed with the same voltages as the C64 and thus it must have already solved that problem: by looking at the schematics we can see that it provides the Datassette Motor pin with an unregulated +9VDC supply derived from the 9VAC rail with a simple AC-rectifying circuit that we can copy straight away.

(Incidentally, the C128 is also fed with the same voltages as the C64, despite using yet another connector. Thus, if all the serious Commodores live with the same voltages, why should we be different?)

While the AC-rectifying circuit is pretty textbook and only consists of a bridge rectifier and a few smoothing caps (one of which is laaaarge!), I also carried over the power input filtering circuit, and it wasn't easy to fit everything in the small space available on the board (while respecting all the indications from Edoardo :D) but, again, we made it:

You might have noticed that the Plus/4 uses a line filter that looks vaguely similar to the one used in the Amiga 500 & friends. Thus, it felt natural to replace it with the same Laird filter I used on Rämixx500, which helped a lot since it is a bit smaller.

Something more worth mentioning is that while the C64 actually needs the AC signal (it uses it as a known frequency to feed its Time of Day timers with), the C16/LittleSixteen does not. This means that if you are not going to use the Datassette port, you should be able to get away powering the +5VDC rail only.

Anyway, for completeness's sake, I will also design a simple C64-style power supply. One day.