That’s gonna be hard to fit in the original case…
It looks like a drone battery, where the stated ability to do a high rate discharge can be an advantage. In a goTenna, it’ll burn down in case of a short
Or maybe not. There are ways to provide protection if a battery doesn’t self-protect in some manner. And not every short is created equal.
Rather than bust open the case and void the warranty, why not just use a battery pack and the provided power connection of the GTM?
Not sure about the dimensions on your battery, but a battery pack might even take us less space in cubic inches. I’ve been using these battery packs that are labeled as 20,000 mAh (they’re not), but which were sold as 8,000 mAh (sounds about right). I can power a GTM for a week on one of them. I just ignore the solar panel, although it’s a good backup to have for field use.
The key to it working is that it stays on even when the GTM current draw is very low. The always on feature this facilitates is a desirable one to look for in battery powerpacks to use with the GTM.