On the MX5200 & 5800, one dealer (salesman) told me that there are 4 settings for widths & another told me the R4s aren't adjustable widths. Which is correct? If adjustable, what setting would you recommend for 50% use on a semi-steep mountain property & 50% use on a semi-flat farmland property. Another ? - one dealer said they fill w/ rim guard/beet juice & another said methanol & water. Which of those is better or are is it 6 of one / a half-dozen of another?