Copied and pasted the info on Digi's wall like you requested, although that said, maybe you could help out by giving me an idea of who the major pushers are for Garren as secondary Rider so that I'll know who I need to convince.
Obviously, there's a clash of interests in regards to who is Blade's Secondary Rider, so I'm going to give you my arguments as to why Chalice is the correct option since a discussion will be more useful than an edit war.
Firstly, Garren appearing as the second Rider does not secure him a place as the Secondary Rider because by that logic, TheBee should be considered the Secondary Rider of Kabuto while Gatack is clearly more important than TheBee.
Following on that point, the Secondary Riders are not determined by being the first Rider aside from the protagonist Rider to appear on the show, but by their rank of importance. Chalice is significantly more important than Garren. This is evidenced by how the only two Riders to appear in their Rider forms (as opposed to being only in human form) in the final episode are Blade and Chalice, and that Chalice does serve the role of the Final Boss.
On a more concrete note, the final cast credits for the series, as well as the cast credits on the main website list Hajime/Chalice's name second, while listing Tachibana/Garren's name third. Considering that the cast credits are listed by rank of importance rather than appearance, this is significant evidence that the makers of the show themselves consider Chalice the Secondary Rider of the series.
Also, your arugment that Garren has clash with Blade more than Chalice is inaccurate. In terms of direct physical confrontations in their Rider forms, both have clashed with Blade an equal amount of times in the following episodes:
This list does not include the episodes in which Hajime has clashed with Blade as Joker in which case, Hajime has more conflict with Kenzaki than Tachibana