Questions about approach grafting pines

[Ozz80]

I have a Scots Pine that I pruned to old needles last summer in order to compact it. But it still looks too leggy to me and I am planning to approach graft some of its branches to lower parts of the trunk. Does heavy pruning of the previous season made on donor branches adversely affect the chance of approach grafting? Should I wait a year without decandling and graft those branches next spring?

My other question is whether the thickness of the donor branch affects the success of the graft and if so, what should it be?

 

[Shibui]

My experience with approach grafting pines is limited but I have done a couple and more junipers.
Previous pruning should not affect success of grafts. It's the growth after grafting that helps heal the graft union and your branches should be ready to grow strongly after recovering from the previous pruning.
Thickness of the scion should not affect success but I found it much easier to bend the scion into place and make the graft with scions about pencil thick.
Thicker branches will leave a correspondingly larger scar when they are finally separated which means more years until that heals over.
Really thin scions sometimes do not survive the cuts necessary when making approach graft.

 

[Wires_Guy_wires]

Yes it negatively affects growth, but that doesn't mean you have to wait. This year it'll produce new growth, and if you leave that unaffected it will act like nothing has happened.
The thickness will affect the wound you will have to make, and that in itself will affect your success; a bigger wound will require more healing than a smaller wound and thus will take more time.
Smaller branches tend to fuse or get enveloped faster.

When I approach graft conifers, I let the graft run and keep the rest of the plant in check so the insert gets relatively more power in its growth.

 

[Ozz80]

Many thanks for the help!