This works, but it leaves all traffic between the CloudFront edge node and S3 unencrypted. In theory, that shouldn't be an issue, by why risk it?

A better way is to completely leave the "website" bits of S3 off, and leave that all up to CloudFront. You can create an Origin Access Identity, then grant that OAI access to read your S3 bucket (all automated in the wizard when you create a CF dist and specify an S3 origin). You then specify a default object in your CF dist, and bam, CF is using the S3 REST API over SSL to secure that CF-S3 hop.