What up Pimp; Rusty, everyone...

Okay let me share my [limited] knowledge about Si Blast.
I have a fucking GALLON of the stuff. I'm glad I bought it. How is it that some of the most useful supps under my kitchen sink have that Botanicare sticker on them? lol!

First, you should not worry about P toxicity. I sat down with a calculator and a periodic table one day and figured out how much H3PO4 you would have to add to OD on Phosphate. It was a large number. The trick is that Phosphoric is a tri-protic acid- see those 3 Hydronium ions? That means for every mole of acid you add, you are getting THREE moles of the active ingredient in the pH down. Yay! Don't worry about that pH number. It has little to do with your ultimate pH; especially since it will only make up a negligible % of the total volume of your fert solution.

Si helps plants strengthen their cell walls against heat and cold stress, the resulting water loss, and damage from pests and pathogens. The little buggers'll be chewing much harder to make any progress in eating your leaves, lol!

It may be safely used on vegging plants and is recommended when you expect a heat wave or drought.
I've never flushed preventatively just because of the stuff.
I'd apply it following similar guidelines to calmag, since it is a MINERAL, not NPK or hormone, supplement. So put it in first or along with the calmag. Then add ferts. Then adjust pH.
I would use it at minimum dose if you intend to use it routinely. I avoid max doses of ANYTHING until I am certain that the plants are cool with it. Somewhere in between lies your sweet spot. You may also foliar it from what I am told.
I have never seen proof that it causes lockouts or damages the final product in ANY way.
And I believe it to be useful in temperature stress situations, or if you have mites.

Did you know that Silicon is the most abundant chemical substance on the planet? Yet in its purified form, is still outrageously difficult to come by, and supply problems are THE number one reason that photovoltaic technology is still so FUCKING expensive! There is a big German solar panel manufacturer that was recently trying to offload its New England manufacturing division, but the buyer balked because the Si supplier would not commit to a long-term supply agreement.

So there is your silly factoid of the day. Now go enjoy your weekend, already!!!