SR 4756 burn rate is between WSF and HS-6 and I tested both for USPSA 40S&W/9mm loads and ended up using WSF due to greater flexibility to produce acceptable accuracy down to mid-to-high range load data compared to HS-6 preferring near max load data for optimal accuracy.
I haven't used discontinued SR 4756 but as
@rfwobbly suggested, you can test the start charge and if you get reliable slide cycling and spent case extraction/ejection along with acceptable accuracy, you can conduct powder "work down" instead of work up until you lose reliable slide cycling and/or accuracy.
I tested several other comparable/faster burning than BE-86 powders for 40S&W loads (Herco, Universal, Power Pistol, W231/HP-38, Green Dot, Sport Pistol, Titegroup, WST, Clays, Bullseye, Red Dot/Promo) and if you are looking for lighter target loads, found W231/HP-38 to produce acceptable accuracy below start charge with light to mild recoil and I used these loads to transition 9mm shooters to 40S&W, known to have "snappy" recoil.
With 180 gr plated TCFP and 3.9 gr of W231/HP-38, recoil is lighter than 9mm and 4.0-4.3 gr will produce mild recoil.
If using faster burning powders than W231/HP-38, unless you use lighter start/low charges, recoil will be progressively more "snappy" as burn rate gets faster. But for range blasting general purpose 40S&W loads, if your wife can tolerate 9mm recoil being mild to moderate, can even faster burning Red Dot/Promo work? Yes, with mild to moderate recoil. To me, this is possible due to 180 gr TCFP/RNFP's long bullet base producing sufficient neck tension to allow efficient enough powder burn to produce accuracy.