Here's a sketch with 3 different examples of ways we could present a recurring upsell to readers engaging with our fundraising banners.
In version 1, the recurring ask doesn't happen until the donor has completed the payments form and hit our Thank You page. It is styled as a simple button.
In version 2, the donor selects an amount and payment method from one of our fundraising banners, and then sees an interstitial recurring ask before being directed to payments wiki.
In version 3, the upsell happens thru an interstitial, immediately after the donor has completed the payments wiki process.
Version 3 is our preference.
CC'ing @CCogdill_WMF in case she has any additional details to add.