When two boats share the same hull type — in this case both the Pro-Line 18 Flats 2011 and the Pro-Line 29 Grand Sport 2013 are modified vee designs with fiberglass construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
Size is the most obvious dividing line here. The Pro-Line 29 Grand Sport 2013 measures 29,3 feet overall (2013), giving it roughly 11,0 additional feet of deck space compared to the Pro-Line 18 Flats 2011 at 18,3 feet (2011). Weight tells a clearer story for trailering families: the Pro-Line 18 Flats 2011 tips the scales at 1 548 lbs — 917 lbs more than the Pro-Line 29 Grand Sport 2013 at 631 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
The power gap is worth calling out. Rated to 600 hp, the Pro-Line 29 Grand Sport 2013 has a 485-hp advantage over the Pro-Line 18 Flats 2011's 115-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads — 27 gal and 24 gal — so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Pro-Line 29 Grand Sport 2013 is rated for 8 passengers, while the Pro-Line 18 Flats 2011 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Pro-Line 29 Grand Sport 2013 could be the deciding factor.
Bottom line: Choose the Pro-Line 29 Grand Sport 2013 if your priority is putting more people on the water — it handles 8 passengers and at 29,3 ft it has the deck room to back that rating up comfortably. The Pro-Line 18 Flats 2011 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.