Hyundai Sonata NF 2.4L I-4 Spark Plugs Autolite vs. Denso/OEM (Caution!)

I was changing the spark plugs on my 2009 Hyundai, and following the shade-tree mechanic rule of sanity #407861 (Always compare new part vs old part), I discovered that the new plugs I was installing did not match the old ones.

The new, long plug on the left is a Denso IKH16 5343 ( 14mm diameter, 26.5mm reach) which Denso lists in their catalog for the 2009 (2008-2010) Hyundai Sonata NF 2.4L I4 Engine, while the 2005-2008 NF Sonata 2.4L I4 lists the IK16 (14mm diameter, 16mm reach) in the australlian market, but only lists the IK16 for all years and models of sonata in the US market. The Denso catalog shows american and aussy cars have the same engine codes for 2008-2010, even though they spec different plugs.

The plug on the right, which was installed is an autolite. Autolite says the AP3923 fits/meets OEM for the same Sonata, but also list AP5325 for the specific year. The OEM plugs are actually Densos. 

I screamed inside my heart. Would the pistons crash the plugs?

 The hyundai manual and parts page, at least at the time of writing, isn't very helpful.

The 26.5m plugs threaded in and seated fine. I manually turned the engine over and didn't meet a hard stop.

So, concluding that it at least would not grind the plugs to bits, I hit the starter, and it runs fine. 

Though, lacking specs, I must conclude (a) always check the parts (b) take care before putting in longer plugs. It seems like the engine was intended for longer plugs in some markets and not others.