Hammer Query

I am looking to buy a big-ish rotary hammer with stop rotation to do some projects. I’m looking at the Bosch 11241EVS and the Hilti TE76 or TE55. The latter two I can probably only afford used.

My projects involve chipping: demoing an old chimney and chipping off a level concrete hot tub pad (2 1/2″ thick on the thickest side) from the underlying sloped slab. And simple anchor placement in old slab for securing a new sill plate and some interior partition walls.

Clearly I could set the anchors with a smaller rotary hammer–but I want the bigger unit because I have a lot of chipping to do and I don’t want to futze around with a wimpy chipper.

My QUESTION involves the drilling performance of the bigger SDS-max combi hammers on smaller holes. The Bosch for example lists an Optimal Concrete Range: 1/2″-1-3/8″

What problems (if any) will I run into using a bigger combihammer to drill holes smaller than 1/2″ ?

Roof Issues

I have to span a square of about 50 by 50 feet with a roof. The roof should have a cupola in the middle.

I am wondering if I can simplify construction of the roof and reduce cost by putting up four columns arranged in a much smaller square in the middle of the larger square. These columns would form the base of the cupola and be tied together on the top by a sturdy wooden square frame.

What I am hoping to do is to eliminate large and complex trusses by having rafters running from the exterior wall to the columns and tying into the frame on the columns directly (somewhat like in a shed roof). The cupola will then be erected above the square frame on top of the columns. The rafters would have to be about 25 feet long and span empty space.

If simple rafters cannot span this, would it at least result in less complex and smaller trusses that are easier to transport and handle. Can I do this and achieve significant cost reduction in the
construction of the roof.?

If this particular construction does not work can columns be used to simplify the construction of the roof in some other way?