Lot's of people get shocked over the thought of this.
I called a Comp Cams engineer that I work with and told him I wanted to test a roller cam with hydraulic and solid rollers and gave him the lobes I wanted to use. His reply? Oh, no problem! We use those same lobes on both hydraulic and solid rollers.
I've been using solid lifters on hydraulic cams since the 1970's. With solid flat tappets I just use .004"-.006" lash on a hydraulic camshaft.
