Whether or not you feel that a drain plug magnet is essential, we have yet to see a reason why they would damage a system. If nothing else, they certainly make it easier to identify any magnetic metal particles which are present in the oil when you change it, as opposed to trying to see what the filter has caught! For the CX500 we acquired a magnetic drain plug filter from Wemoto:
Not a great looker – the colour clashes rather a lot with the nice aluminium colour of the engine front cover. The most common question asked so far is, “Can you paint it?” – and we will see how that goes prior to installing it, though I wouldn’t have high hopes of it being a show item by painting it, given how likely it is that some of the paint will be rubbed off during installation and riding.
The magnet isn’t anything earth-shattering – it won’t hold up the plug’s weight – but it’s more than enough to catch small metal particles, as it is designed to do.
We will report back at the next oil change and see what it caught. In the meantime, if you’re not worried about the colour or are willing to try painting/coating it it’s a pretty inexpensive way to get a little bit of peace of mind and an easier way of seeing what sort of metal particles are floating around in your crankcase.