I think you're getting a bit carried away fella. I spoke to St.Mirren at tea time last night and both clubs had sold around 1500 tickets each at that point. Thistle maybe slightly more as the last update they had from the Jags was mid afternoon.
The "South Stand" allocation being sold out is a bit of a joke. I can see the live ticket situation in the South, there are 5 blocks in that stand, three are showing 50% sold, one is showing 25% sold and the other is showing less than 25% sold so if Thistle have sold out their allocation for that stand then it must have been very small.
The North Stand is "sold out" but they haven't sold the first few rows. The stand only has 22 rows so not selling even the first 3 rows reduces the capacity by 13% !
Either way it's clear the Jags are bringing a good support, which is terrific but it won't be anywhere near 3,000.
My guess would be 2,200 Jags on the night, with maybe the same from St.Mirren giving a gate of just short of 4,500. Time will tell !