I know that my experience might not really be that valueable, I don't have any tournaments to back it up except local 4-0 and 3-1 with Boin's list.
Sol Ring is something I rather decided to cut, because usually the deck just simply wanted to play something on turn 1 and if possible not get it countered. I had (still have) Black Lotus in the deck which allows for some t1 TKS or something but usually when I had access to the card a better play was to play a Thorn and following turn I usually had the 4 mana I needed to cast the spell anyway. I lost more games to having Lotus and not a Mox than vice-versa. I run all five Moxen and would not play less. What number of sources is necessary is a question. I think that if the deck won't rely too much on the Eldrazi (Reality Smasher) it does not need to play that many sources, but it still wants to have access to 2 mana on turn one.
I also had Trinisphere in the deck instead of Chalice of the Void and noticed that I managed to win more games because of that Sphere than when I had the possibility to play Chalice.
This deck seemed to want an explosive start the same way Eldrazi wanted and without over 27 sources this deck just can't do that. But it is possible that one does not need that because it is more of a Prison deck than stompy. Sitting behind Thorns works as well and is usually safer than wondering if your opponent has the Force of Will or not. It's not like 1 TKS will certainly win the game.
I actually like Recruiter of the Guard in the deck and will have to try it. It may not be as crazy as in Legacy but being able to find a hatebear seems pretty good (or an additional creature).
I struggle with Shops but maybe I'm doing something wrong. :-/
What I wonder is why Boin likes Vryn Wingmare. I played that before but Thalia, Heretic Cathar often has similar effect since many decks run fetchlands and nonbasic lands but also affects creatures coming into play. The card has First Strike and is quite a beater unlike the Wingmare and can block Foundry Inspectors/Fleetwheel Cruiser and other creatures all day. The only downside I see is that Thalia is a legendary creature so you can't have two in play and it can be bounced with Karakas...
(time to try wappla's list instead)