I haven't had a chance to finish mine up. I intend to just shim the convertor slightly with washers, then trim the midplate to allow the starter to bolt directly to the transmission. When I get a new convertor, I'll just have it made with thicker pads. I think that'll work fine with my .120" midplate.
Since yours is 1/4", I'd definitely make sure (a) the convertor fully engages the pump with a spacer like you said, and (b) the starter gear fully engages the ring gear on the convertor. Maybe do what my plan is and just trim away the starter mounting area of the midplate, so it mounts directly to the transmission?