T&G wood panels installed in diaganol pattern on a wall

I started to install "roofers"(3/4 by 5 1/4 with smooth side out) planks on a long wall with 2 windows at an angle such that they meet in the center of the room creating a downward looking arrow pattern....sort of a herringbone? Anyways, I completely installed the left side of the room without too much hassle. I started in the far left bottom corner and worked out from there to the center of the wall. This was fairly straight forward since I could tap the end of the planks to meet exactly at the center line on the wall. From the right bottom corner it was also easy going until I ran into the long boards that run from the center of the wall to the ceiling...I'm lost as to how to get these boards to meet exactly in the center as now I do not have anywhere to tap the boards to the center line once I get the boards onto the tongue and tap into place the downward movement of the board leaves a gap in the center of the wall. This would not be a problem if I intended to cover the center line gap with a vertical strip but I would rather not. Any suggestions on how to "move" these boards to the center line once they are joined to the lower board's tongue? I'm considering some sort of dry lubricant applied to the bottom tongue after perhaps sanding some of the tongue down to allow me to shove the boards to the center line???