Chris J Dixon wrote:
I have a Bosch ART 23 Combitrim which uses nylon line 1.6 mm dia.
There is also the option of a more robust 2.25 mm line, but this
comes in precut fixed lengths, with a central metal crimp, and
fits in a different spool, to be used double-ended.

http://www.espares.co.uk/part/trimmers/bosch/art-23-combitrim/p/1082/856/0/1061165/1117056/extra-strong-23cm-trimmer.html

In terms of line wear, the thicker line is, unsurprisingly, much
better, but the price of the precut lengths is prohibitive.

It would clearly be possible to buy a length of thicker line and
wind it onto the standard spool. I can see that auto feed would
probably not work, but when does it?

About the only practical downside that I can see is that the
thicker line would produce greater unbalance forces when in use.

Has anyone else beefed up their strimmer line, or got thoughts on
why it might not be a good idea?

Tried it. Yes it ******** up the autofeed and it also breaks where the line
exits the spool. Also inside the spool the line rubs together on the coil
and adjacent turns friction weld to each other.

There doesn't seem to be an advantage to using thicker line on a strimmer
not designed to use it.