Rally template: What code can I inject to have a thumbnail image at the top of each blog post?

Hi there,

Firstly, I just want to point out that I've asked Squarespace Support this question, but they cannot advise on custom code injection. I've put the chat transcript below in case that helps other people with this same question. I've also searched this forum, but couldn't find an answer :(

My problem: I'm using the Rally template (Brine family), and I'm keen to have my selected thumbnail image for each Blog Post to appear at the top of each individual blog post.

Does anyone have a code snippet I can inject under the Blog Settings > Advanced > Post Blog Item Code Injection section? (Or is there another area I can do this?)

I've tried this snippet that I found in this forum, but to no avail:

<style>
 .view-list .excerpt-thumb {
 display:block !important;
 }
</style>

Thank you in advance!

PS. Here's the chat transcript in case it helps others

(11:34:59) Tyne Z.: Okay, so according to the style tweak options for your Blog Page within this template, (which you can view here https://support.squarespace.com/hc/en-us/articles/227054767#toc-style-blog-posts), it appears that automatically placing the thumbnail image in the top of the blog's page isn't a feature included in this template.(11:35:16) Tyne Z.: We therefore have a couple of options--(11:36:21) Tyne Z.: First, you could go back through and upload the thumbnail image as an image block at the top of each blog post in the blog's content(11:38:07) Heidfi: Option 1 sounds painful :((11:38:20) Tyne Z.: Or second, you could consider switching to a template where the blog's thumbnail is automatically in the top of each blog post. Skye is an example of this type of template: https://skye-demo.squarespace.com/(11:38:48) Heidfi: Thanks Tyne... bummer(11:39:01) Heidfi: Option 2 is not ideal, either (we just switched from Skye hehe)(11:39:14) Heidfi: So, inputting a code snippet won't work ?(11:41:12) Tyne Z.: I see! Unfortunately, in that case, there's nothing we can do on the built-in end other than manually inputting the images. Although there isn't a built-in way to place the thumbnail at the top of each blog page, you absolutely may be able to accomplish this using custom code. I would like to note that we don’t offer support or troubleshooting for custom code. While I can't offer more help on this topic, there are many resources available that can point you in the right direction. Personally, I would suggest our Answers forum, which is a place for Squarespace customers to collaborate on code modifications as well as ask questions about coding that we, in Customer Care, may not be able to assist with. Here is a link to take you there: 
 http://answers.squarespace.com/ If you can't find an existing post that answers your question exactly, I'd recommend creating an account and posting your question. Here is a guide that covers adding custom code, should you choose to go that direction: https://support.squarespace.com/hc/en-us/articles/205815928-Adding-custom-HTML-CSS-and-JavaScript(11:42:23) Heidfi: Thank you, Tyne. I understand your limitation here. I'll give that a shot.(11:42:49) Tyne Z.: Okay, best of luck! I hope the Answers forum is helpful :) Is there anything else I can help you with before we wrap up today?(11:43:56) Heidfi: That's all for today(11:43:58) Heidfi: Thanks for your help