I am presently shooting a 550 grain arrow out of my 49 lbs. at 28 inches Striker Extreme recurve.I draw around 27.5 inches and always try to limit my shots to less than 20 yards.I am shooting Carbon Express Heritage 90s cut to 28.5 inches with a 250 grain broadhead (Magnus 2-blade plus 125 grain steel adapter).I am planning an antelope hunt this fall and want to use a little lighter setup arrow-wise to flatten trajectory since I know its highly likely that any shots may be a tad longer. I would like to stay with the Carbon Express Heritage arrow and possibly even with the 90s size.Also probably a 125 grain broadhead unless something else would be better.Anyone have any suggestions to what length I would need to leave the arrows?
Also what length do the Heritage Express 90s come in full length? Seems I recall they come in two lengths uncut? Anyone have a similar setup?
Would a lighter setup be too low in poundage for a 30 yard shot? All advice appreciated.

Get a full-length shaft, put a standard insert in it with whatever point you want to shoot, and trim down 1/4" at a time until it shoots how you want. Every bow is different, as is every person's release, so you'll have to find out by trying.  I shoot CE Heritage and can say that 1/2" can make a huge difference in either direction, so it'll take you tuning it to your rig.

As far as trajectory, I just did this in the other direction, adding 100 grains to my arrows (up to 600 grains now) and yes, there's a little difference at 30, but I've given up 20 fps in favor of momentum, and I still hit 30 pretty consistently shooting instinctive. It's mostly about how well you judge distance and how practiced you are at that distance. Practice A LOT at whatever max. distance you plan to shoot. I'd really hesitate to shoot 35 at an animal even though I do it all the time for 3D. My 100 grain-heavier arrows do drop off noticeably faster as I approach 40 yards, but at that distance I'm gapping anyway and not shooting at critters.

As to poundage,  plenty of hunters on here will say they've killed deer with 450 grains from a 47 lb recurve.  There's also a 12-grains-per-pound crowd.  Once the arrow is launched, it's not losing much momentum between 20 and 30 yards, so it's more about how accurate you are with a given trajectory.  Hope this helps.

When the 90's first came out they were only 29" long,but the new ones now come 30.5" long.They take their own nocks and inserts,they are 9/32 so the heavier brass inserts will not fit unless modified.