Try kneeling while having your legs held together.
From there it's easy to adjust the height and also the "deepness" of penetration.
Very comfortable and stable.
Also I find that men love this position.

With your legs open you can get slippage, fanny farts and too deep. The more the legs are closed the less all of this is.
You can also have additional control from how your upper body is positioned from resting on hands all the day to face on the bed. This changes the angle in which he's penetrating and can be used to stop the cervix getting hit.

Do you have a guy in your life that you could practice with? Google all the various ways for doggy including using pillows etc and have some fun.

There's no rule to say that your legs have to be open and legs open/closed does give you both a different sensation.

If their legs are on the outside, which seems to be the common position, I close my legs together. I am very short and doggy is generally painful for me because they hit my cervix, especially larger cocks. I find by closing my legs, it stops them going in so deep. Sucks for them most likely but I wont be in pain for any amount of money.

If they are too large, I just wont do doggy. Some of them are well aware they are hitting me and go "ohhh what's that in there". I reply rather flatly, "that would be my cervix, and it's rather painful".

This is me exactly Veggiegal.

Even when i am on top, i can often feel their cock hits my cervix..and don't get me started on when they wrap my legs over their shoulders. I literally seize up and thrust them out again with a spasm ( great for the ol' pelvic floor  )

The only good thing for me about Doggy is that it tends to be over quick 

Doggy can be either legs in or legs out. If a client is slipping out a lot, it's either the case they're doing too big thrusts, or my pelvis is tilting down too much, so I put my chest down on the bed, which pushes my hips higher and positions me more upright.

If you find you're getting your cervix hit too much, don't be afraid to pop a beppy in, I do that occasionally with some of my more well endowed clients. It gives a cushion over my cervix. You just have to lube it up a lot more than when you're on your period.

I am always a bit reluctant to do doggy, as I had a guy do this too.

I always put his penis in myself during ALL positions, but am particularly vigilant with doggy-making sure to
Check for any meddling beforehand.

 Never trust a client, however well you think you know him 

I dont really like doggy unless they have a smallish cock but i find if i curve my back and pelvis under a bit it stops them going too deep.

Definitely. Cat posture for the big ones, cow posture for the little ones .

Legs inside for me too, because I'm also a shortarse.

Some guys are just rubbish and doggy and insist on trying to mount you, which never works because of the angle. The most comfortable for me is when they're kneeling up and sometimes I will have to direct them on doing this.

Yes - that winds me up... Just do it properly, FFS!