I am in the midst of installing a new bathtub (fiberglass) and the flange for the drain pipe is about 1/2 to 3/4 of an inch too low. My question is do they make a flange extender or an extended piece that screws into flange (i have one that is brass - threaded inside and out - that came with my drain stop, but it's too short given how low the drain pipe sits).

I have a concrete slab and I really don't want to replumb the entire drain pipe if I can help it. I guess I could cut the ABS pipe where it comes out of the T and use two 45 elbows (in a S shape) to bring the pipe up to where I need it. Does anyone see a problem with this? The tub (alcove) is already installed and I don't want to pull it back out if I can avoid it (because it's a pain is the a$$.

Thanks in advance.