Been through this a few times. However, first, to remove speakers stuck with Blu-Tack, twist them around their vertical axis, they come off quite easily.
Size of the blob can be important . . . a very small pea in each corner, with the speaker well!!!! pushed down, distance in, less important but the 'BT' spreads, you dont want it to come to the edge, looks ugly.
Those that say blob size dont make any difference, nine times out of ten, it does, too much and the base often goes soggy, the image gets vague, the speakers can sound generaly wooly . . . Try it, if you cant hear any difference you have lost nothing have you . . . IMHO, over many years of making and selling stands, its as important as getting the filling right. That may be a problem, getting the filling right . . . took me a long time to arrive at the right formula.
CJSF