Your limitation for height will be the power chord.
"ust want to let everyone know the Lighthouse power cable length is 8 feet long or 2.5 meters."
Source: https://steamcommunity.com/app/358040/discussions/0/365163686048992255/
In the general stance of HTC, higher is better. you will get better tracking.
In the extreme example of "Well, let me go up 10 meters!" is that the higher you go, the smaller effective max room-scale space you will have. what the numbers are on this, I don't know. (and not sure it matters in this case.)
But back to the practical notes...
Fact is, the reason for the height is for the light houses to see all possible parts of the user. SO, raise your hands above you're head, and jump. This is the height that the Lighhouse needs to be able to see and track. (if you plan on jumping in VR.. not recommended.)
Can you put it up higher? Yes.
Will there be side effects? As long as you can get power.. maybe, but not enough that you will notice.
My suggestion:
If you have a huge room, test out your max space before setting up. See if you can borrow (2) tripods and setup the room. See how the performance works.
ALSO!!
(key safety!) Make sure you use a stud-finder that has current detection before mounting your light-houses.
::My Setup::
I hope this helps. I have mine at about 8-9 ft with no problem.
The main factor that you'll run into is running out of VIVE cabling before you run out of space.
HAVE FUN!!!
(and Rec Room is AWESOME!)