Have taken a good number of measurements and based on my daughter's pedal to saddle position both of them will be sitting above the rack while my better half has legs nearly as long as mine and will be well above the rack.

Have seen children as young as 4 years old riding this model and could see no issue with the rack stays and can see it serving as a back rest if it was padded...

If it was a problem I could have the stays modified when the bike goes back for more brazing and a new coat of powder.

Should have the bike built and out for test runs in about a week as I have sourced the parts I need and am just awaiting delivery of the stoker stem, rear section, and matching fork.