Maybe he will vomit more maybe he will vomit less. Trying won't do any harm. Prepare two bottle, one as usual, the one without the carabel and instead of 250 ml water, 300 ml water.
IF you have read a bit the NZ website about reflux, you will read that thickening agent can make things worse, because in case of vomit, they will stay in the oesophagus for longer and increase the pain. It is not as straight forward as it may seem.
Reflux is so complicated and frustrating.It is an umbrella term for many pains. We had the feeding ultra sound done, he had his meds yet for 8 months he cried non stop. The mother is alone, completely in the dark, with a crying baby who is in such pain.
Walking and patting, rubbing, his back and bottom for at least 30 min after feeding helped a bit. Sitting on a sofa with him straight and rubbing wouldn't work, it had to be walking, which at 2 am is pure torture.
It got worse with weaning, then round 8 months it started getting better. HE was at that time tested for allergies, and put on a no dairy, no wheat, no eggs/chicken, diet. This didn't mean he was fine but he was a lot worse when he was eating these foods.
Around 2y, he started eating these again and now he is a strong, happy ten year old. And I always used to say that he never cries because he had cried all the tears his body could produce in the first 8 months of his life. HE has some allergies nut not to the foods he needed to avoid. He is extremely allergic to penicillin, probably from having so much in the first months of life when vomit would enter lungs, ears during the choking episodes and cause infections. Also cats and hay fever. He also developed asthma when we moved in Oz. Despite this he is a sport star in athletics and swimming.
I also used to give him some fennel tea with a spoon, not in a bottle.