Good job. I'm an "as long as it works, as long as it serves the purpose" type myself. Good job.

Once you have it up and running you can always adjust and make improvements. The first carpet mill frame I made had a ton of 'adjustments' and 'improvements' to axle diameter and axle/roller location. I drilled and re-drilled so many holes the end of the mill looked like I hit it with buckshot. It was a mess. But it got better and better.

The oak slats may be heavy but you can always run them thru a table saw and then plane them to a thinner/lighter slat. Since it is working I would do that before I went to a bigger wheel.

Either way, good job. I always like 'doing it myself' vs. spending a boat load of cash. EWO