In February 1943 CMHQ did a study which showed it was feasible to put either a 17-pdr or a 3.7 inch gun in the Sexton.
In May 1943 DND's Directorate of Artillery proposed a 3.7 inch assault gun on the Grizzly platform - as it would have been lightly armoured it would have been more like a Nasehorn than an Elefant. None of these studies raised any concerns about using the 3.7 inch in a a direct fire role. In an anti-tank role, the 3.7-inch round could penetrate 90mm (at a 30o angle) at a range of 2,000 yards.
More details will be forthcoming in "Secret Weapons of the Canadian" Army
www.servicepub.com