I have a X99 ATX mother board / 6950X processor / 128 GB of 3200 RAM and want to SLI two RTX 2080 ti cards together.  The functionality of the board limits where the second graphics card can go.
Essentially, Slot 1 and the 4th Slot are the best options.  There is little room for air with the 2.75 wide / three slot cards.  Was wondering if a two slot 2080 ti card could be in Slot 1 and the three slot 2080 ti card in the 4th Slot.  With a 3 slot SLI bridge.  
 
The cards would have slightly different clock rates.  
 
Looking at using 
in the 4th Slot and 

in the 1st Slot.
 
That should provide some air flow for both cards.  But, are the cards going to play well or fight?
 
 
 

I have the GA-X99 Designare EX Rev 1.0 Mother board.  
There are a series of implications if different positions are used.  I do not have any other cards other than the graphics cards, but do do have a M.2 card running.  
I have a 4 hard drives, two optical drives, and a number of external data connections. 
 
I understand the slot "Number" vs "Position" are different.  The original intent was to use the first two positions for the two slot card, have an empty position for air, then a three slot card.  With one position empty before the Power Supply.  
 
Thanks for the help.  
 

Can I use a SLI bridge between a two slot 2080 ti 11 GB card and a three slot 2080 ti 11 GB card?  Both cards have two fans.  The documentation seems to suggest the only difference is the cooling fins and the fans.  The clock speed is slightly different on the two stock cards.  I have read that the two cards should be identical when using a SLI bridge.  Are the two slot and three slot 2080 ti two fan cards "identical enough"?
 
I appreciate the help on the mother board and agree that two three slot cards will work.  But the question remains, can a SLI bridge be used between the two and three slot versions of the two fan 2080 ti 11 GB cards?