Third consecutive attempt at pumping. This time used a soft rubber cockring around scrotum and grasped hold of it to use as anchor point. Pulled it away from my bosy and went into the cylinder almost fully erect.
Was able to pump up to 300-330 mmHg. Glans had good expansion, almost 6.2” at least. Saw a transverse line forming on the lower aspect of glans. Could be a potential spot for blister formation later. Overall, happy as able to pump smoothly thanks to the sound advices above.