The second dataarea in the current scv.xml is already defining the extra 4KB ram.
Quote

<part name="cart" interface="scv_cart">
<feature name="slot" value="rom128k_ram" />
<dataarea name="rom" size="131072">
<rom name="polepos2.bin" size="131072" crc="cb69903d" sha1="472900d7b7fa6cdf30014731dcc925ef5ca65499" offset="0" />
</dataarea>
<!-- 4KB RAM on cartridge -->
<dataarea name="ram" size="4096" />
</part>