Hahaha, the tennisballs are there because my equipment is laying on each other in my shed and this prevents collepsin my footstraps so they stay in the right shape this way... i also keep this explaning to people when i am on the beach hahaha lol.
I must say about the tri-fin set up that i also find it a little to sketchy and i prefer it as a quad, then it is a dream

But i have to say i set it up in the tri fin set up with small and flexie fins.
For my quad set up with the quadster 67 witch has 7-13 fins i used for a while K4 7-12 but now i am back to 8-13 witch are perfect.
For my 74 i use K4 9-13 (8-13 will do also for 4.7 and smaller) and the same for the quadster 79... You can nicely tune the boards with the fin positions from loose to more grip but i always think the looser the better but that's personal.
The back fins are placed far to the outer rail for more grip btw.
In quad set up the board is so good and fast in the turns but always with total control... the board keeps going faster and has lots of grip but still it feels loose in the turns, all this together is a fantastic feeling...
And because of the control you can also let the board go free full throttle (overpowered) and look for that steep wave to get some airtime...
@gwanso, if you have the financial opportunity then i would go for two boards...
Remember the quadsters plane really really fast and you don't want a to big board in my opinion. For example, i plane with my 4.7 on my quadster 67 just as fast then on my 74 or 79 but then again i am only 63 kg.
My friend is 85 kg and have no problem what so ever to get the quadster 79 going so don't be afread that that board will be to small and when you are going to use it it will be windy so i would say go for that one mate.
The 79 is really 81 liters according the german (surf.de) test so i would take that one for sure.
Next to the 79 i would go for the 91 to get a big range out of your quiver and it will be superb with your 4.8 , 5.3 and 5.8 sails in light and medium winds. On the 79 you can use your 3.7 , 4.2 and 4.8 powered up but it also take a 5.3 very well. I think with 5.3 winds tho you would like to sail on the 91 for some extra float.
Like i said the boards really planes very fast and are also very controlable in the high winds and they give lots of float. The turn on a dime without any effort and are super loose.
Trust me you won't regret getting these boards and i am not saying that because i sail Tabou but i really mean that. My (85 kg) friend has two quads from other big brands witch i will not name and he always want to sail my 79 when its windy so i think that said it all... to go to your question about the quatro LS 95 i think it will be a good board too but i haven't sailed it so i can't comment on this one.
I would suggest the quadster 79 and 91 for sure.
Hope this helped.
Grtz, Martin