Of the 118 or so readers who have taken the cubes test, 14 have reported credible Wechsler full-scale IQs in Canada/the U.S./the U.K. within the last decade. These are are their scores:

cubes raw scoreWechsler IQAge when taking the cubes test
10144Thirties
6120Twenties
9133Late teens
7133Twenties
8137Fifties
11149Twenties
10160+Twenties
17160+Twenties
893Below 16
5143Undisclosed
2103Thirties
7120Twenties
9142Twenties
11124Twenties

There mean cube score of the sample is 8.57 (SD = 3.46) and the mean Wechsler IQ is 133 (SD = 19.5). By equating these statistics, cube scores can be converted to IQ equivalents:

cubes raw scoreIQ equivalent (U.S. norms)
17181
16175
15169
14163
13158
12152
11147
10141
9135
8130
7124
6119
5113
4107
3102
296
191
085

When I ran a regression equation, I found that each year older than 25 decreased cubes IQ by 0.5 points holding Wechsler IQ constant, thus I tentatively suggest older people add a bonus of 0.5 IQ points for each year above 25. However this suggests either massive age related decline and/or the Flynn effect and more research with older subjects is needed because this bonus seems a little generous.

The correlation between cubes and self-reported Wechsler is 0.61 however this needs to be corrected for extended range (since the IQs of the sample are more variable than the general U.S. population).

Grady Towers supplied a formula for correcting for range restriction, which I assume I can use since extended range is simply negative range restriction:

Correcting for extended range reduces the correlation from 0.61 to 0.52. However we should also correct for the fact that the Wechsler IQs were taken as much as a decade ago and thus would only correlate perhaps 0.8 with what their Wechsler IQ would have been on the day they took the cubes test. Dividing 0.52 by 0.8 gives 0.65 which is probably a good estimate for the cube test’s g loading.