Hey dring44...
If there's one thing in life that I have learnt - is that what works for me might not work for you, but here's my 2c anyway...
I recently got into both straps, so I hear what you are saying... All the below is based on me at 84kg, JP Super Sport Pro 118 and (usually) a 7.4 KA Koyote.
I'm certainly no expert on the fine tuning of your settings, but what they guys have said so far is spot on... In regard to boom height, you need to get the boom height up to a point that you are able to transfer the weight when you are hooked in. I had my boom sitting in the lower half, and when I was told to raise it an inch - which basically took it to the middle of the cutout, the effect was immediate. I was able to get much better weight transfer which (at that stage) helped me to get settled and plane upwind.
I usually get hooked in, slide the front foot in virtually straight away and after a second or two providing I think there is enough wind to keep me planing, get the back foot in. This was only two sessions ago, we had a 15-20kn day and I took one look down at my back foot and just popped it in...

You said you have your back foot behind the mast ? I take it you mean your front foot, with your back foot between the two straps... so is that your back foot between the back straps ? I found I needed to slowly work on getting my weight back as I got powered up. Put your weight back too early and crapola you sink the tail and round up into the wind. (I'm sure you may already know), you need to counter the rig... so when you want to put weight back, take the sail forward, helping you also bear away as you do

.
Are your lines long enough... I found nice long lines 28-30's are helping me get hooked in, sink my weight down and keep my arms straight to hike out. Get your front foot in... point your toes to accelerate (ala Cribbie advice) and get your back foot backwards... when your back foot is basically sitting right next to, touching or even better - on the back strap - you know you are ready to lock yourself in !
Hope this helps as the difference in getting both feet locked in has been amazing... sailed 64km in a session last weekend and didn't want to get off the water ! I also found I got better efficiency too, as in I was able to post better speeds from lower winds than I have in the past.
Hope this helps mate.