  The VERITAS Imaging Atmospheric Cherenkov Telescope array (IACT) was
augmented in 2019 with high-speed focal plane electronics to create a new
Stellar Intensity Interferometry (SII) observational capability (VERITAS-SII,
or VSII). VSII operates during bright moon periods, providing high angular
resolution observations ( < 1 mas) in the B photometric band using idle
telescope time. VSII has already demonstrated the ability to measure the
diameters of two B stars at 416 nm (Bet CMa and Eps Ori) with < 5% accuracy
using relatively short (5 hours) exposures. The VSII instrumentation was
recently improved to increase instrumental sensitivity and observational
efficiency. This paper describes the upgraded VSII instrumentation and
documents the ongoing improvements in VSII sensitivity. The report describes
VSII's progress in extending SII measurements to dimmer magnitude stars and
improving the VSII angular diameter measurement resolution to better than 1%.
