SP Twin Jet size question

I returned my full foot Twin Jets size 9-10 as they were too tight.
I got open heel version in size 10-11. My shoe size is 9-1/2. When wearing the open heel with 3 mil Mares low top boots (just doing warm water dives for now), the straps are pretty much all the way adjusted for fit and the square back at the bottom of the fin is almost even with the back of my heel. Does this seem like an Ok fit/size?
(they feel great, and getting in and out of them is much easier than the full foot)
I will more than likely start doing some cold water dives (California), with 7 mil boots. Any thoughts?
The exchange was through LP, so they might get a little concerned if I keep exchanging.
(one reason to buy from your LDS, but can't beat their prices).

Note: I did buy my BCD, weights & regs from my LDS

David

The key thing is not to have your heel hanging off the back ... we see that often, and that they are not so tight that your feet cramp.

MyDiveLog:

The key thing is not to have your heel hanging off the back ... we see that often, and that they are not so tight that your feet cramp.

Click to expand...

That makes me feel better, I think I'll go put them on now.
It really cracks up the wife when she comes home.