Dicky,
I too use a Speeco quick hitch, cat I. My RFM is a Woods RD60 that works great but QH use is difficult. Woods offers a kit to permit QH use, but it involves replacing the top mount struts with chain links so it pivots forward and rearward. I called the engineer and asked about an alternative. He said you could use the Speeco optional top link like the LandPride one and try it, but watch carefully for interference.
I did so and found the only thing to worry about is contact between the mower driveshaft and underside of the QH horizontal bar. The RD60 is unusual in that the gearbox mounts about 2.5" higher than the JD and less expensive mowers. The LandPride horizontal bar is rectangular instead of square like the Speeco so there is more room under the LandPride QH for the driveshaft.
So far, my driveshaft and QH are happily married. I shorten the top link so the QH leans forward a bit at the top, that gives enough room for the mower flexible top mount and the Speeco top link to pivot freely. My lot is fairly flat and smooth so I don't have much opportunity for the shaft and hitch to hit. If you have more offset and rougher mowing it could be a problem. Being careful and mowing slow is fine with me. Keeps me from having to do other honey-dos if I sit longer on the tractor.
The only other thing I find about attachments and QH's is you need to buy a QH with an adjustable top hook. Many of the smaller or cheaper attachments don't use the regulation distance from lower pins to top pin. My KK carry-all requires me to use the top hook holes and the JD and Woods attachments require use of the lower hook mounts. I removed the bolts and use hitch pins of the proper size with lynch pins. I don't do a lot of heavy twisting with attachments like discs around corners, etc. so I don't worry about the hook brackets getting bent without bolts.
