I think you will be fine. If you want to be sure, measure how far down your water level drops when power is off to your main tank. Use that to calculate the volume of water that drains to the sump. There are aquarium volume calculators online. So if your tank is 72 x 24 and the height drops 2 inches, your volume of water would be 72Lx24Wx2H = 15 gallons (approximately).
Next, measure your sump. Your sump probably has a set water height it runs at or may be adjustable. You're interested in the remaining space. Trigger 34 sumps are 34"x15"x15" I believe. If you run an 8 inch water height, you will have 7 inches left. Use volume calculator. 34 x 15 x 7 = 15.45 gallons space available. Of course, this is just an example and not completely accurate, as you need to factor in thickness of the acrylic and glass (ideally you want to use inner dimensions) and height of your return chamber is likely different than the rest of your sump depending on how you have it set up. And, as others have stated, you will want to position your return nozzles such that they do not cause additional drainage (or use a check valve, but I'd do both to be safe).