Trouble with after-purchase one-click upsell setup - Need code to add to website to pass through a hidden field email address to allow one click add to purchase


I am trying to setup a true after-purchase one click upsell following Infusionsoft instructions: I have a “trip-wire” product order form, whose thank you page will be the landing page for my One Click Upsell product. However, it will require the email address of the purchaser to be passed through to the Infusionsoft webform via a hidden email field and the interruption of a third party landing page (whether a website page, Leadpages page or even the Infusionsoft Landing page as that builder is contracted through a third party) between the first order form where the purchaser purchases the trip-wire product and the html code that embeds the infusionsoft webform on the nice looking landing page breaks the process and the email is not getting passed through to the hidden field. The setup does work if I send the customer directly to the Infusionsoft webform but that’s not a decent solution given the inability to format/style a nice looking landing page and format the webform to be responsive, etc.

The instructions in the Infusionsoft article I followed for this setup (One Click Upsell after a purchase | Max Classic) point out that “This will only work when using the Max Classic - hosted version of the web form. The web form can be added to you web site and hosted by you using the HTML or JavaScript embed code, but doing this requires that custom code be added to your web site that auto populates the hidden fields for email address so the web form can identify who to add the order to. This custom code is not provided by Keap.”

So I am seeking feedback from anyone who might be able to help me code that on my website (or if there’s a way to make it work on a Leadpages or infusionsoft page). If anyone can offer any insights, referrals or advice, I would be very grateful. I have a promotion ready to go if I can get this issue solved!