Yes, but as long as you do the following:
- Use the latest stable releases of SafeA9LHInstaller 2.x.
- You use the two payloads of the same group (no mixing two payloads).
- Use the latest stable versions of the payload.
Sounds scary, yes, and I was scared of updating myself. But
Plailect's guide is very well-written, makes sure you get the latest versions and gets you through it really easily.
On the software side, SafeA9LHInstaller is designed to prevent most bricks, and actually updates payloads very quickly.
I'd also suggest updating your system too, if you haven't already. If you're on A9LH, you don't need to stick to an old version since A9LH protects you from most bricks and custom firmware will protect your A9LH from being deleted by the update. If you're scared about it, back your NAND up using Hourglass9 then use Luma3DS to update as it always protects the FIRM partition from being written to and it never gives the option to disable it.