The real problem isn't the plant (except that it is an indeterminate rather than a determinate). It is the method of support you are using. Far better methods are available, ones that would allow the plant to do what it does naturally with no problems. The other alternative when plant height is a problem is to grow only determinate varieties. In other words choose plants that fit your support options rather than trying to force the plant to fit, OR change your support methods to fit the plant's needs.

Add to that the fact that the more you prune an indeterminate plant the taller it grows to compensate for the loss. That is what topping does. New growth doesn't develop low on the plant - that part has what it has - and if you cut off those top long branches two new ones sprout from the node just below the cut and they grow tall. Cut them and 4 more take their place etc.

Lemon Boy, even though it is an indeterminate, is not normally considered a huge plant when compared to many other varieties. Yours is rather leggy as if it isn't getting enough sun and that fact only adds to the height problems.

So solutions - since it is too late now to change to a different support system, you can buy additional cross bars for those type cages (they come in packages of 6) and you can wire-tie additional green poles to the existing ones thereby creating a much taller more sturdy cage. Or your fence top has lots of places to tie branches to for additional support and you can them encourage it to drape back down this side of the fence and keep growing. You can also cut a piece of metal fencing, tack it to the wood fence and create a taller trellis. Or you top the tall branches, trim them down to cutting size, root them and have new plants to plant elsewhere to get more fruit. Or you can top the plant and keep topping it and accept the fruit amount you have now will be about it.

Next year I'd suggest either growing determinate varieties - many good ones - or research the many other options for creating a good support system. There are lots of discussions here about the various methods, many with pics.

Hope this helps.

Dave

thanks for the info, ya i did not know there were other methods besides the typical cages and what i got, but again i dont have to much experience. last year it basically went over the fence and back down, like you mentioned. which i didnt mind to much. but ya, i guess the legginess comes from the fact of the fence being where it is blocking some sun, just hope the main stalk wont give in on me. i sadly cant remove the fence

thanks