Toobs are possible to clean up.....to a point and will look acceptable in a day or so of effort.
The good thing about a Searider is that it will last for decades , so if the tubes hold air you can always retoob em in a few years if you so desire.
David Manning renovated my Sea rider ( and damn near made a silk purse out of a sows ear) He used Hypalon paint on the rubbing strakes which hid a few years of use!
I am presuming the hull is sound!
Re the excessive weight I guess the following might account for it:
the transom has to be substantially stronger to hold the extra engine weight and I presume that whatever that attaches to (the Hull) has also to be stronger to handle the extra forces generated by the engines
The boat is wider at the rear and the tubes are bigger
I would also imagine it would have inboard tanks
I have an Avon searider project to work on over the winter. It's a six metre and in a bit of a state, I'll keep you posted!