I'll echo Rich's comments regarding your report. Nicely done.
I love what Regrowth does to the Gushbond engine. It helps make it incredibly consistent. Regrowth basically functions, once Gush is found, as a Merchant Scroll, but one that doesn't reduce the density of Gushes in your deck.
When one of the So Many Insane Plays started talking about abusing it with Gush, generating two mana, using that to Regrowth the Gush and casting Gush again netting me 2 cards for 2 life and potentially upping my effective Gushes to 8, I was intrigued about this interaction and started building decks. Then I came to a grinding halt. I didn’t know how to build a deck like this, I was not playing pre 2008 restrictions. My experience with building decks has entirely been in the Dark Confidant era (I started playing ~M11/Scars). My most recent experiences with Gush have been RUG Delver and Cobra Gush which were very different to what I was trying to accomplish with this deck.
Since you mentioned our podcast, I should tell you that my latest
set review spends a few pages discussing my preliminary testing of Regrowth in the Gushbond engine. In addition to Preordains, which you'll find gives you more consistency, I suggest a few other cards you might wish to test as well. For example, I've found Imperial Seal to be very good with 4 Regrowth.
Also, you may wish to consider checking out my
Gush book. It was published in early 2010 and revised in early 2011, but alot of the principles remain the same. Also, I've been working on an update with latest decks (will probably be published this fall), and everyone who got the 2nd edition will get the 3rd.