SwitchableSusie, my wife also loves that sexual position you describe where your legs are together and your husband straddles your legs. The Kamasutra call this the Twix position, and it's superb for clitoral stimulation. See:
http://sexpositions.club/positions/151.html
Whenever Pam and I are in the Missionary Position, Pam almost immediately uses her arms to lift my legs up and spread them out so she can close her legs together below me. Actually, she's not that strong. She only does part of the lifting and spreading, but it sends me the message of what she wants, and I easily do the rest almost instantly. We've got the Missionary-to-Twix transition down pat.
The clitoral pressure in the Twix position is huge. Pam gets off almost totally by clitoral stimulation, which is why she loves it. For that reason, I developed a Twix variant that I have just dubbed the Flying Twix:
Instructions for the Flying Twix position:
1. Optional for maximum effect: Man and Woman remove all pubic hair and cover their pubes with a generous amount of a heavy oil based lubricant such as 90-weight gear oil--just kidding--such as mineral oil or olive oil.
2. Start in the Twix position.
3. Man places hands on either side of Woman
4. Man uses arms to push his upper body into air so it makes no contact with Women.
5. Man lifts legs into air, completely off of Woman's legs and the bed.
6. Man slides his pubic area, back and forth over Woman's pubic area by pulling and pushing with arms while alternately and rapidly (a) lifting legs higher and bending knees, and (b) lowering legs and kicking them out straight.
Since over half the man's body weight is supported purely by his pubes in contact with the woman's pubes as they slide back and forth over each other, the clitoral stimulation for the woman is off the charts. (Fun for the man too.)
I can only sustain the Flying Twix position for about one minute at a time between resting periods in the normal Twix position. Fortunately, one minute is plenty to send Pam screaming into orbit!
It's quite the workout.for me. Since discovering the Flying Twix position a few months ago and Pam's consequent insatiable craving for more and more Flying Twix minutes, I've noticed substantial new muscular development in my arms, legs--especially my hamstrings--and my butt and lower back.