You're being grossly misled....The LAST thing you want is a flail mower. Unless you have time to waste, MONEY to waste, and HP running out your ears, a flail would be a serious mistake.
I own and operate a mowing business where large tracts of land are our specialty. I've tried flail mowers. I went into that phase with a predetermined notion that I could market that as some sort of "advantage". It didn't take long to recognize I'd made a mistake. Currently, we operate 7 tractor /mower rigs with 15' rotary batwings, 2 rigs with 20' rotary batwings, 3 rigs with 7' single spindle rotaries, and 2 with 6' rotaries. We commonly mow tracts of commercial real estate of several hundred acres, have a number of highway right-of-way contracts, as well as doing property maintenance on my own farm. I'll give you facts, not the "pipe dreams" of a few "dreamers" who mow just a few acres with no consideration to time OR cost.
For the record, my business mowed over 17,000 acres in the past season. My experience with flail mowers is based on 5 different models of various sizes, ALL in the top end of cost/quality, and used to mow approximately 1,200 acres during their time with me. (2 seasons past) My numbers are based on REAL WORLD operation, and not just a bunch of sales propaganda from someone who seems to have a serious case of tunnelvision.
Flails require more HP per foot than a rotary cutter, OR, be prepared to mow at a MUCH slower ground speed. (as an example, we were mowing very successfully with an 85hp tractor and 15' batwing (rotary). In the exact same conditions, 16' of flail mower was struggling along at roughly half the ground speed while on a 155hp tractor. (requiring a MUCH more costly tractor as a power unit) THAT fact has to be considered when figuring "initial cost")
Flail mowers are MUCH more costly initially.
Flails require a much higher overall long term maintenance cost.
Flails have limitations as to "conditions". You DO NOT want to mow grass that's even a little bit wet. You're more or less locked in to mowing short....Try to leave grass a bit longer than "scalped" and they do a miserable job (at best)
As you go up the charts from an entry level mower to a commercial grade mower, the cost of a flail mower goes through the roof! Commercial grade flail mowers are INCREDIBLY expensive, as is their maintenance and replacement parts. And by the admission of the sales person handling the demo, USED commercial grade flails, once showing significant wear, have a lower rate of resale worth compared to a rotary cutter.
I demo-ed several of the best flail mowers available, operating them along side of "mid range" (cost) rotaries. The rotaries outperformed the flails at a huge cost difference. Time (per acre) was nearly double with the flails. The final cost of operation (per acre) ws so disproportionately high for the flail mowers, I would have effectively been putting myself out of business.
Get a 10' or 12' drawn type rotary single wing (batwing) mower, save yourself a TON of money, get the job done faster, save yourself a ton of hours of routine maintenance, and do just as good (if not better) of a job. Long story short....a well maintained rotary cutter will provide an excellent quality of cut, and do so faster and cheaper.
There's a perfectly good explaination why over 95% of commercial mowing is done with ROTARY mowers.....Nothing else works as well, nor does anything else do so in such an economic, efficient manner.
A 10' rotary, behind a 50hp tractor, mowing normally maintained grass could reasonably expect to safely mow @ 4mph (ground speed) That would allow you to mow 50 acres in 11 to 12 hours. With a flail mower, you would struggle to mow @ 2-1/2 to 3 mph.....with a 7' or 8' mower behind that same 50hp tractor. With that, figure closer to 22 to 24 hours of mowing time for 50 acres (on average). Qualify THAT by considering your cost of purchase to be 50% to 100% higher for a commercial grade mower (rotary vs flail) and operational maintenance in a commercial application can be (usually IS) nearly double.
Based on the FACTS, no one with even a shred of "business sense" would want to mow with a flail mower. Even the sales person who was in charge of set up and demoing the flails I tried was convinced it was a pure and simple WASTE OF MONEY to use a flail in a situation where a rotary was (more than) capable of doing the same job.