I have been using the stem style TPMS on bikes & cars for around 10 years and have only ever used rubber stems and on bikes with heaps more "giddy up" than a Strom and I have never been concerned.
My Garmin system asked for steel stems (I did not use steel), Tyredog and the other system I linked do not.
This has been discussed on this site before and I did post up the weights of the senders of the 3 brands I use for those interested.
The stems on my Strom are quite short but the ones on my box trailer are very long, designed to extend past dress rims, the stems would be over 10 years old and I would have no concerns about towing that trailer.
Change your rubber stems every time you change your tyres and you should never have a problem.
Some of the 19 rides in my shed
2014 V2, Snoopy
2009 Wee, Pumbaa the pig
WR450F, The Blue Postie Bike
YZ250N smoker with rego, Stinky.
Yamaha MT09 (FZ09), The Scud missile.
Club Lead not Club Med.
He with the most toys wins.
Out of my depth in a puddle.
Live life on the edge you will see more that way.
Ridding a motorcycle keeps things in balance.
At the end of each trail and at the end of each day history is made.