Getting ready to transplant outside- question

My seedlings are about ready for transplant outside- they've been hardening off for several days, will be hardened off for a few more days and then will be planted. They appear nice and strong and have been responding well to being outside- I notice drastic growth over the past day (they like the sun). They are tallish and I was hoping to reduce their size somewhat so that they will have a stronger stem- I've already repotted them once into Forestfarm Ocean Harvest up to the cotyledons and was wondering if I can now plant them in the ground, bury the cotyledons and plant about an inch below the first true leaves.

Will covering the cotyledons smother the plant? Should I just stick with planting up to the cotyledons?

Thanks for the input!

How old are they? how many nodes?
sounds like they are ready to be put outside to me, plants love being outdoors.
burying the stem is a good idea , i usually bury mine to their first set of true leaves. Over time the stem should grow roots out of that stem to help secure it. It will not smother it.
got any pics?