I tested the PRG-UNV when it first came out, and that was my top complaint. It is a VERY capable mount. So, it's not going to drop the projector, but I didn't like how it didn't seem to be able to lock in as tight as the Chief RPMAU mounts are capable of.
I used a Chief RPMAU with my DLA590 and as has always been the case, it does lock in extremely tight, while still offering some worm-gear style adjustments.
Of course, the Chief RPMAU runs even more than the Peerless.... so, there's that. In reality though, I buy the Chief off of eBay when they come up and I typically get them for well under $100. Sometimes brand new in the box.
I wouldn't say you should return it. Certainly not if you aren't getting all your money back. But, from the start I always recommend the RPMAU over the Peerless because I simply have not seen a better mount on the market to this point.
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That's a complete unit, but you can get the RPM mount by itself, or used as part of a complete setup for not that much...
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Then you need a SLBU (universal bracket) to go on it, or order a custom plate specifically for the JVC if you want. I use the SLBU...
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Be aware, that the keyed locking systems such as the RPMA, RPMB, and RPMC models actually use a slightly different SLBU than the non-keyed/locking models...
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So, you would need an SLBU which has studs instead of screws. In fairness, I've actually never tried to use the SLBU with screws on the locking series of RPM mounts. They may work just fine!
Worth noting that the custom bracket for the NX7/RS2000 is the same that JVC has used on their older models, so it is the 281 custom interface bracket.
I've picked up many Chief mounts over the years in various configurations and I've always used them in my installations. I've only used a non-Chief mount a couple of times, and I always regretted it. This includes the Peerless, but I've used cheaper ones and they just get worse and worse.