I can understand the reason behind your idea, but having driven DHC's since '88 I don't see the problem. If you put a new roof on the car with the OS fixings, just be careful when you raise or lower the hood and it will be fine, even in winter [;)]
<center>

<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (not very well known yet, but back on the road)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC
http://tr7beans.blogspot.com/</i>