Boysenberries -cut back vines?

I can't believe I'm asking this -- talk about stooopid...
Is one supposed to cut back the vines after bearing? If so, how far? Or?
Neighbor gave me several plants years ago as b'day gift. Now they have taken up residence all over the garden, and are waving long, spiny vines at me. Getting a few berries, but should be getting more (yum!)
I want to centralize them in one area where they can climb up a trellis but do not know how/whether to cut back.
This is So.Calif coastal.
TIA
HB
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Update: Sorry, should have checked before posting. Here's what one Web site said:
"Boysenberries berries grow profusely with horizontal vines. After harvesting, the biggest job a gardener or a farmer has to do is pruning. After effective pruning you will prepare your plant for the next growing season.
* Do not prune boysenberry plants in the first year after it is planted, let it produce fruit and grow as much as possible. Prune it in the next year. * Use bypass pruners to prune all the fruit bearing canes. Cut down the canes to 2 inches above the soil level. * Tie all the new fruit bearing canes to a trellis. Use a string to attach the new canes carefully to the trellis. * Remove the tips of the new fruit bearing canes in mid summer. This method of removing tips encourages lateral growth in the plant. * Cut the side branches of the new fruit bearing canes of the last season. Cut these branches so that they remain 1 foot long."
***Now I am somewhat intimidated. *** Looks like even 8 or 10 plants would need a LOT of horizontal space. This is where your feedback can help me. Also, do you have any disagreements with quoted procedure?
Mucho TIA
HB
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