I suggest you try the JMW that comes with the table. If you like it, you could save a lot of work.
The HRX does not come with interchangeable arm boards. The arm is mounted in a hole drilled through the three-layer (plastic, steel, plastic) plinth. (I understand that the proper drilling of this hole is a serious machining job.) The JMW arm is physically larger than the Graham 2.2 and most other arms (probably including your SME IV). In order to use another arm, you need to have the hole drilled in a different place, and that place has to be precisely located to fit your arm. Your arm manufacturer needs to communicate with VPI for this. With the Graham 2.2, a little platform of a particular height is needed as well.
When I bought my HRX, I ordered it without the JMW, and I requested that it be drilled for a Graham 2.2, which I now have mounted on the HRX. As a result, I can assure you that VPI has been sent the specs for locating the hole for the Graham 2.2. I can attest that the HRX sounds very good with the Graham. Of course, I have not been able to compare the sound with the JMW or the SME arms. I explained my rationale for choosing the Graham over the JMW in a previous thread (try an Audiogon search for HRX). I have a Graham Phantom on order, with an understanding that it will fit into the same hole as the 2.2. I'll save the dustcover saga for another occasion.
Good luck.
The HRX does not come with interchangeable arm boards. The arm is mounted in a hole drilled through the three-layer (plastic, steel, plastic) plinth. (I understand that the proper drilling of this hole is a serious machining job.) The JMW arm is physically larger than the Graham 2.2 and most other arms (probably including your SME IV). In order to use another arm, you need to have the hole drilled in a different place, and that place has to be precisely located to fit your arm. Your arm manufacturer needs to communicate with VPI for this. With the Graham 2.2, a little platform of a particular height is needed as well.
When I bought my HRX, I ordered it without the JMW, and I requested that it be drilled for a Graham 2.2, which I now have mounted on the HRX. As a result, I can assure you that VPI has been sent the specs for locating the hole for the Graham 2.2. I can attest that the HRX sounds very good with the Graham. Of course, I have not been able to compare the sound with the JMW or the SME arms. I explained my rationale for choosing the Graham over the JMW in a previous thread (try an Audiogon search for HRX). I have a Graham Phantom on order, with an understanding that it will fit into the same hole as the 2.2. I'll save the dustcover saga for another occasion.
Good luck.