@rickytheevangelist oh boy my time to shine.
First off -NOT- a groomer, but a havanese owner who has spent the last year trying to figure out what type of cut works for our guy that still feels havanese-ish but is something that I can keep up with maintenance brushing in between the groom sessions.
One, find a picture of a cut you aspire to and talk it over with your groomer, take a deep breath because its a journey they may not get it right the first time the key is communication and its only hair.
Two when you pick up your Havie and its not just right, live with it and make a quick note of how it grows, what works for you and what doesn't and then talk about it at the next groom. I have always found it easier to show my groomer what I DO like than tell them what I don't as soon as I get them. As an example I know that our guy is the perfect length about a week after his groom, so its easy to take a picture to show them next time.
Three is trust your groomer, how short he comes back to me like getting a test grade because I am learning where his mats hide and how to maintain them. Also ask them for help for how to maintain it in between, like what tools or products can help you. Havies, like poodles have hair and requires dedicated grooming and a solid schedule to prevent them from getting pelted.
And lastly, our guy has ended up being much shorter than I aesthetically prefer but he is cute as hell and its at a length I have time to keep up with. I also have an excellent groomer and have developed a solid relationship with them and feel comfortable asking to try new things and they are just as comfortable letting me know if its going to be more work on my end or is just plain stupid and I love them for it.