Good compatible carts for RS Labs A-1 tonearm?

I just finished my Lenco 78 slatedeck and have an RS-A1 tonearm ready. I've heard of issues fitting some cartridges. Any suggestions on reasonably priced mm or high output mc carts that align well with this tonearm would be greatly appreciated.
The major problem mounting cartridges in the RS-A1 is that its headshell has threaded holes. Moreover, there is no room to use conventional screws that would enter the headshell from above, because of that cylindrical housing that houses the headshell pivot point. Ergo, you are limited to cartridges that have no threads in the mounting holes and that permit space for screws that will have to be oriented upward, so that the threads of the screw engage the threads in the headshell. I have not made a survey, but it seems to me that this limits you to using mostly MM cartridges. Most MCs in my experience have threaded mounting holes. That said, I was successful mounting an Ortofon MC7500 in my RS-A1, by mutilating some stock headshell screws and then physically holding the cartridge and headshell together as I screwed in the screws from below. It works OK. You also have the option of drilling out the threads on any cartridge to make it work with the RSA1; I did not care to do this to my Ortofon.

As for mating based on tonearm effective mass and other usual parameters, the RS-A1 is so unorthodox in design that I have no idea how one would estimate its effective mass. Moreover, the designer seems to be claiming that such considerations are rendered moot by his distincitive approach. Despite all of the above, I really do like mine.
It is an interesting observation that mm carts "tend" to be threadless and mc carts the opposite.... wonder why that is..
I never had a problem mounting threaded carts on my RS-1A. I used a Te Kaitora and a Shelter 901. As long as you can put the screw up from the bottom of the cart, it will work. This rules out wooden Grados and Kontrapunkt/Jubilee, for example, with mounting holes that don't go all the way through the cart body.
You can use threaded carts with the A1 arm, but the level of 'tightness' of cart body to head shell will be determined by how tightly you can hold the cart to the shell while turning the screw through the two threaded holes. i.e., as soon as the screw head 'bottoms out', that's as tight as you can go.

The alternative is to drill out the threaded cart holes which has the effect of turning the headshell threads into nuts.
Thank you for your responses. I really wanted to try a Grado, but that won't work. I'm going to use some of your suggestions and try a Clearaudio Aurum and a Denon 160 and see what happens.