A recent experience with Sunwing-
Just as a comparison I flew with Sunwing last year to Panama City and I will probably look for other options when I go to Panama again. They are inflexible.
The maximum weight allowed was 2 pieces and a total of 20KG which is very limited depending on the purpose of your visit. On the way to Panama City my luggage weighed 20KG. Therefore on the way back I knew I would be over. Flying back home I was 5KG over and I was charged $9.00USD per KG thus $45.00USD total. In addition to the weight restrictions the airport procedure for Sunwing in Panama City was horrible. Very slow and they manually checked (wrote up the baggage tags) for a full plane of passengers. This is the downside when you fly with some charters, lower fares but poor service.
Hopefully someone will comment on Sunwing to the DR as I usually fly direct to SD non-charter flight. However, I am sure the weight restrictions will be the same.
-LDG.