Looks like you and I are trying to do the same thing.
It seems that your simply looking to poll modbus registers, and write them.
Here's what I found.
There are two types of groups.
Group one are experts at doing just this.
Group two are experts at taking the data and putting it on a slick graph.
I spent 6 months on this same project last year, only to get frustrated and quit.
I think we should collaborate.
Drop me an email response.