It's safe. Those bags aren't going to put much if any, stress on the frame. The only thing I would recommend is buying tape to cover up the paint where the bag touches the frame. The rubbing will dull the paint. I use this stuff:

https://www.amazon.com/X-Treme-Tape-TPE-X36ZLB-Silicone-Triangular/dp/B00HWROLIG/ref=sxin_3_ac_d_rm?ac_md=0-0-c2lsaWNvbmUgdGFwZQ%3D%3D-ac_d_rm&keywords=silicone+tape&pd_rd_i=B00HWROLIG&pd_rd_r=d518d7e9-c4e9-438d-a40f-a90937f876d2&pd_rd_w=0NmAq&pd_rd_wg=IpCCn&pf_rd_p=6d29ef56-fc35-411a-8a8e-7114f01518f7&pf_rd_r=VS9YFJBF1MVZ04YB8FPY&psc=1&qid=1574198327

The units: https://smile.amazon.com/gp/product/B07JH276KY

I held the bottom in with a couple wraps of this: https://www.amazon.com/X-Treme-Tape-TPE-X36ZLB-Silicone-Triangular/dp/B00HWROLIG

Then just used 2 more o rings on the top part (but down below where the balls/heat are).

Kinda bunged up the DC port but you get the idea. Took about 10 minutes all told. Nice upgrade from my mason jar lol.

In use: https://streamable.com/63540k