I'm looking for anyone using the Holland hitch to pull their 5er. Do I have to make any modifications before using a Holland?

You probably should consider a "air pen box" or "air hitch" Class 6 through 8 truck running gear is for heavy loads. The Holland and Holland is mounted to the frame of the truck. Most 5th wheel RV arn't heavy enough to "work the suspension, so road shock/bounce etc! is transfered to the towed unit.
We have just started a conversion of a class 8 tandem axle and have opted for the air pen box.
$995 VS: $2250
Scott, Barb, & Mutley

I have the stock hitch on my Volvo 610 (Suzy Q). Suzy Q pulls a 33 foot toy hauler and had covered 15,000+ miles since April of this year. That mileage covers freeway, back roads, off-road (and one no-road).

Zero issues so far. I'm pretty anal about maintanence and check for frame issues in the regular pre-flight inspections.

I know others argue good points about going to an RV type hitch. For my own needs, I can't justify the replacement and work involved for switching hitches. Others, with a different setup and different driving style / needs, find the RV hitch is a better mix.

You can go stock or after-market. It depends on your own requirements.