Tomatoes can be topped by cutting them a short distance (~2 cm) above a leaf node. It does cause tomatoes to focus energy on lower parts of the plant including fruit and stems. Once done, you'll need to do it again periodically on "suckers" from the plant as they grow taller.
Are you currently cutting the "suckers" off the tomato plants? Are the plants determinate or indeterminate varieties (or both)? How far apart did you plant the tomatoes?
It appears your weather stays right in a good zone for tomatoes all summer long. Topping them now would likely reduce the yield. However, if you've planted them with a lot of distance (~1 meter between plant) then topping will cause both the fruit and the "suckers" to be more active which would allow you to leave the shade netting where it is and still get a decent harvest from the fruit the grows on the suckers.
If you are planting close together and have been pruning suckers, you could consider raising the shade netting as an alternative. Otherwise you will be reducing the yield from the plants. Pruning on top - "topping out" a plant - is generally something to do closer to the end of the season.