There are a few questions that come to mind. What is the amperage rating of the reducers? They put relays on horns because of the amperage pull.
I don't think 12 v would be a problem for the horn as long as it's not prolonged use. Another option would be to series the horns. IF you only have a single connection on the horn, you would have to open it to see if there is a chassis ground in the horn.
Larry
