Replying to Tail press

I've been attempting to do these all season and every time I try to do them on boxes or just like cruisin across flats it kills my knees or calves. I can get my tips up about like 10inches or so but i feel like i should be able to get them higher. My friend was telling me my boots might be too stiff. My boots are kinda shitty and i've had them since i was 14..so theyre 4 years old but i don't think it would make that much of a difference. but im probably wrong. I'm probably just doing them wrong too but any tips on pressing? haha I feel like it should be really easy...